GELASSENHEIT — in other words, ACCEPTANCE
Wilhelm Schmid was born in Germany in 1953. A philosopher by training, he continues to lecture in philosophy today. His books, published in 13 languages, have sold close to a million copies, with 18 of them translated into Turkish. One of them, Mutsuz Olmak (the Turkish edition of High on Low: Harnessing the Power of Unhappiness), happens to be on my desk right now. Perhaps I’ll share more about it with you another time.
Today’s theme is staying calm as we grow older. In his book, Schmid uses the concept of Gelassenheit. I believe what he means is “ACCEPTANCE” or “SURRENDER.” But when translated into Turkish, the meaning isn’t easy to capture. Does it simply mean to remain calm, or rather to embrace life as it is? To me, ACCEPTANCE is the ability to live every moment, in all its highs and lows, in its full reality, with peace of mind.
The author reflects on his own life in the book: his admiration for his mother as she aged, his search for meaning in his own life, and his admission that only at sixty did he begin to understand what it truly means to grow old. He even confesses that, even now, staying calm is not always easy for him.
We know aging is often seen as something to resist. But Schmid argues that the obsession with staying young and the desire never to age robs life of its meaning. Life, he says, only gains true value once we accept its temporary nature and learn to deal with its challenges. The purpose of his book is to change this mindset and to show that aging is an essential part of the art of living.
Personally, I believe life is rich enough to bring new passions and new meanings at every age. And I interpret ACCEPTANCE at each stage of life as the ability to live consciously, meaningfully, and with full awareness. In earlier times, this was called tevekkül, or submission.
Can we learn to become calmer as the years pass? Can we accept life’s natural flow? Can we embrace both the beauty and the struggle of aging at the same time?
Life, after all, is our journey in the time between birth and death. Just as we knew nothing of life before we were born, nor do we know what lies beyond death. But we believe, as our Creator has revealed it to us. Our hearts find peace, we feel safe and assured.
So, we don’t say, “What else can we do but SURRENDER to fate?” We know better: where our strength ends, destiny begins. Alims once said, God’s knowledge follows what is destined to happen (*).
(*) For example, when an astronomer calculates the exact date and time of a solar eclipse, that is knowledge. The event itself, when the sun is eclipsed, is what is destined. So, knowledge follows what is destined. If destiny followed knowledge, then once an astronomer knew the exact date of an eclipse, the sun would have to be eclipsed on that very date. But is the sun eclipsed because the astronomer knew it would be, or did the astronomer write it down because he knew it would happen? Of course, he wrote it because he knew. (https://lnkd.in/dk8eyqbT)
Note: This article was originally published on August 17, 2025.
Every stage of life has its rhythm. Recognizing this matters deeply for our inner world. The ability to remain calm is part of that recognition; life itself can be seen as a single day with morning for beginnings, noon for intensity, and evening for the harvest.
The first quarter, youth. You believe anything is possible. You try, you fail, you learn. Time feels abundant, opportunities are everywhere, and the sense of “I can do it” is strong—though goals are still unclear. In my youth, I felt not only that I could save my country, but perhaps even the whole world.
The second quarter, your thirties and forties. Energy still runs high, but now responsibilities and decisions enter the picture. “I can” gradually gives way to “I must.” One feels the need to build, protect, and sustain. It’s also the time when you realize some of the dreams you once built have now been left behind. Along with what time gives, you begin to notice what it takes away. Schmid argues that the pressure of this period comes from trying to do too much at once, as if we are constantly trying to finish things, always in a rush. I remember when my first child was born at 35, I realized I could no longer pursue every idea that came to mind.
The third quarter, aging. With the fifties, our view of time begins to change. In Schmid’s words, the years that remain are fewer than those already lived. Aging is no longer something distant to be expected; it becomes reality. The focus shifts from the future to the past: “What will happen?” gives way to “What has happened?” At this stage, I felt the need to plan the rest of my life, to think about institutionalization and about preparing the next generation.
The final quarter: old age, seventy and beyond. Activities slow down, and one begins to feel the passage of time more closely. It’s a stage when you can look at your life from the outside, when the past becomes clearer. Not being able to do certain things as before, or having to leave some things behind, gradually becomes natural. Accepting events as they are, leaving life to its flow—that much-talked-about state of calm—perhaps comes closest in these years. I haven’t lived that stage yet, so I can’t say. But I do know this: life has its own plans. I strive with all my strength, but in truth, what I am really doing is running after destiny. And I ask myself: would it be better to simply watch destiny’s plans unfold?
As you can see, Schmid’s perspective and mine diverge in places. Each stage of life occupies the mind with something different; each comes with its own confusion. But doesn’t there come a point when you must set aside what you’ve gained or lost, end the quarrels, and embrace the stage you are in?
Our Prophet advised: be prepared for death as if it might come tomorrow but live with determination as if you would never die. In a hadith, he even said, “If the [Day of] Resurrection were established upon one of you, and in his hand is a sapling, then he should plant it.”
Key Insights into the Stages of Life and Aging
According to Schmid, the second step to calmness lies in recognizing the unique traits of aging and living in peace with them. The third quarter, your fifties and sixties, can bring its own kind of happiness and fulfillment. Why? It is then that we clearly see that life is not infinite and that the road ahead is shorter than the one behind. At first glance, this may sound discouraging, but it is precisely this unpleasant reality that makes the remaining time more meaningful.
At this age, some of us panic and feel the urge to start over. We may end old relationships to seek new ones, abandon unfinished projects to chase fresh dreams. But what good does this urgency serve? For aging means truly knowing life, understanding how things work. Instead of rushing into the new, we draw on our experience to live more calmly, more deliberately.
My late mother had a powerful intuition—she could sense what was coming, a keen judge of character who could spot a person’s flaws from a distance. My late father, on the other hand, how I wish he could have told us in advance what awaited us…
Schmid highlights four guiding concepts: to compensate, to concentrate, to select, and to optimize. These are concepts we have already absorbed through experience and put into practice by instinct. In youth, we jumped at everything; now we know better what matters. We act with greater calm and discernment. This level of awareness, achieved with age, is actually a form of wisdom.
Of course, the visible signs of aging are there too. We notice our hair thinning and turning gray, the lines deepening on our face and hands. Physical discomfort grows, energy declines. We find ourselves pausing to catch our breath on stairs we once climbed with ease. Here, Schmid makes an important point: instead of stubbornly resisting these signs of aging, we must accept them. For no matter how much we resist, life will continue on its own terms. This is something we must fully grasp.
By the time we reach our sixties, reality hits even harder. It’s no longer possible to keep postponing things. Those goals we told ourselves we would “one day” pursue must now either be done or let go, because opportunities, resources, and time itself are shrinking. The mind begins to focus on different questions: What possibilities still remain? What can I still do? What do I truly want, or not want, anymore?
Schmid calls the keyword of this stage “still.” As we age, people around us begin to say: “You’re still doing so well for your age,” or “You’re still very energetic.” Such remarks can be irritating. Yet rather than fighting the word still, it is wiser to meet it with calm. Because much is still possible: calling someone you love, apologizing, reconciling, thanking, sharing, traveling, discovering. These moments deserve our appreciation. My mother used to say on her way back from the corner shop: “This, my son, is wealth, when the prices we pay don’t trouble us.” But she never bought out-of-season or imported produce; she waited for its time. She would add, “We are incapable of true gratitude,” then conclude: “But now, we have given thanks.” For her, awareness alone was enough. As for me, I apply this to all stages of life and all my endeavors. When I reach a new place, a new opportunity, a new achievement, I say Mashallah la quwwata illa billah, meaning “How beautifully God has created; there is no power and no strength except through the Almighty.”
As time moves further on, we find ourselves thinking more often about the past. Missed opportunities, old resentments, happy moments, they all resurface in our minds. Even though the decline of strength and energy feels discouraging, Schmid advises us not to strain our bodies and minds with what we can no longer do, but instead to use the strength we still have wisely and to move without haste, with calmness.”
On this point, I both agree and disagree. In my view, regardless of age, a person should always push themselves. Especially when the body feels tired, but the spirit is still restless. Where the body sets limits, the soul “still” wants to act, “still” wants to accomplish. Nothing should simply be abandoned. To say, “Let me be content with whatever is left in my hand,” may sound mature, even wise, but in truth it is a needless illusion. For if you go to bed weary in the evening yet rise refreshed in the morning, it means you have “still” got it in you. Only, do not overstrain yourself during the day. I once had a Cherokee Jeep; it was not very fast, yet at top speed the odometer showed 20 again because the needle reset after completing its cycle. Today, I believe it is enough if the speedometer simply points ahead, as if only halfway down the road.
Habits
Habits are what bring order to our lives, give us a sense of familiarity, and perhaps most importantly, free us from the constant burden of decision-making—they define the general patterns of our behavior and thought. Especially as we grow older, adapting to something new becomes harder, and instead of adjusting, we often prefer the comfort of what we are already familiar with. Schmid notes that these habits are among the things that make life easier as we age. But in truth, habits serve us in every stage of life.
Could we go an entire day without relying on our habits? Surely, that would be very hard, as most of our daily flow passes almost unconsciously thanks to these habits. They conserve our energy for what truly matters. Try a simple experiment: when you put on clothes, you probably start with your right side first. Next time, begin from the left, and you will see just how valuable your habits really are.
But habits do more than simplify life; they also give it meaning, the author notes. Think of your home. Is it the four walls that make it a home, or the habits you’ve built within them? When you move into a new house, or even spend time in a holiday place, it doesn’t feel like “home” right away, does it? That’s because the habits that turn a place into a home haven’t yet formed. That is also why, in old age, leaving behind familiar places and routines feels so difficult. The author truly sounds like an old man 😀 Similarly, on my weekly goya, I often wake up trying to remember which city I’m in. Especially in hotel rooms, even finding where the light switch is can be a challenge. Yet I believe these moments are what make life rich. Even my wristwatch is a brand where you can’t tell the time at a glance; you need to think about it for a moment.
Are all our habits good? Certainly not. Some are harmful, even irritating to those around us. Yet even when we know this, we may not want to let them go. They are part of what makes us who we are. But the bad ones also make us worse. If you ask me, what truly matters here is to recognize which habits we should keep and which we should abandon, and to act with wisdom.
Physical Pleasures and Happiness
The next step toward calmness is learning to notice and consciously enjoy sensory pleasures, because with age, the senses begin to dull. The details we once overlooked grow more precious as we get older. The song of a bird unheard all winter, the scent of blossoms in spring, the riot of colors in autumn, the snow in winter, all gain new value. Knowing that any of these moments may be the last only deepens their meaning.
The author also speaks about the relationship we form with memories. In youth, we look ahead, but as we age, we look back. Recalling the past may bring some melancholy, but more often it brings peace. Understanding which stories are complete, which were left unfinished, and which belong behind us brings a form of wisdom. At this point, Schmid reminds us that nostalgia is sweet, even sustaining. Old photo albums transport us back in time, and in turn, the past becomes something we can recall with a gentle smile.
Another source of joy is conversation. Especially as we grow older, the desire to share increases. We carry countless stories, but not everyone is willing to listen. In fact, one of the greatest lacks in old age is a willing ear. Accordingly, Schmid insists we must never give up the habit of dialogue, whether at home or at work. Sometimes thinking aloud, sometimes dreaming aloud, can be healing. As for me, I choose to share my reflections, my faith, and my experiences drawn from what I’ve read, whether they resonate with others or not.
And what about sexuality? Schmid addresses this directly. He accepts that with age, sexuality changes form and priorities shift. Less frequent, perhaps, but deeper. Sudden excitement is replaced by calm sharing. Relationships begin to thrive not only on physical intimacy, but on other layers as conversation, partnership, and emotional connection. As we grow older, we also learn the relief of letting some things simply be. No comment!
Pain, Sorrow, and the Rest
With age, the value of health becomes starkly clear. What we once did without a second thought now requires effort or caution. Tasks once handled in a moment now call for planning. We pay more attention to eating well, moving regularly, and surrounding ourselves with people who lift us. Yet despite our best efforts, it isn’t always enough. No matter what we do, the body slows, people leave our lives, and health does not remain perfect forever.
The likelihood of encountering pain and illness increases with age. This is why Schmid emphasizes our relationship with suffering and loss as another key step toward calmness. From a simple shoulder ache to the greatest tragedies, our capacity to accept what comes is tested as the years go by. His advice is this: don’t panic, but don’t pretend nothing is happening either. Be prepared. One of humanity’s greatest fears is to face something for which it is unprepared.
But what if the pain or the loss is permanent? Then medicine, therapy, meditation, and even surgery may be needed. Yet Schmid’s main focus is on how we integrate this pain and loss into life itself. If constant struggle no longer brings gain, then perhaps we must learn to make peace with our pain, even befriend our missing part. Not easy, but possible and necessary, for pain and loss undermine our sense of independence and our desire for control, striking us at our most vulnerable point. Indeed, attaining true “calmness” requires learning to give up this obsessive need for control. From that point on, the aim is to experience life as deeply as possible. Instead of fighting what has befallen us, sometimes it is wiser to accept it, or even go a step further and embrace it, internalize it, and say: This is how it is, and this is who I am. By accepting yourself as you are, you gain a source of strength that no one can take away from you. Questions like “Why me?” “Why now?” “How long will this last?” lose their weight. Consider this: there are those born and raised with far greater limitations. Other creatures, take insects, for example, exist at entirely different levels of life. Gratitude for what we do have allows us to live the moment fully, tasting its richness, even drawing meaning from our pains and losses. If certain movements are beyond us, or if we must live with restrictions, we can trust in our Just Lord to make up for these in the next life. That knowledge alone is enough to make us give thanks today.
For me, prayer and worship remain the greatest sources of strength in this regard.
Contact and Closeness
Contact is one of the steps toward calmness. Schmid reminds us that this need is present from birth through every stage of life, like a newborn settling when it rests against its mother’s skin. As time passes, the need takes different forms, but it never disappears.
To touch and to be touched… Sometimes all a person needs is a hand on the shoulder. With age, such contact becomes more precious, yet also more infrequent. As we grow older, our social habits change, and so does our skin. Some people keep their distance for fear of intruding; sometimes, we withdraw into ourselves. Schmid says older people, in particular, suffer from this.
Beyond the physical interaction, there is also a mental dimension. Conversation and sharing are another form of contact. Moving toward a common thought, even if we do not interpret the same words in the same way or at least reflecting on the same themes or looking at the same view, all creates a sense of closeness. As we grow older, such contacts become more meaningful. Schmid sees them as part of that same “calmness.”
Our Prophet taught: You are all brothers. None of you has superiority over another. Love one another for the sake of Allah and let each of you tell his brother that he loves him. (Tirmidhi, Zuhd, 54).
Belonging, Love, and Bonding
Schmid argues that relationships, especially those grounded in love, friendship, and belonging, are what keep us tied to life as we age. At a time when one turns inward and both body and mind slow down, a bond with another person can be the strongest source for both sustaining calmness and keeping life meaningful.
Take children. In one conversation, when Schmid asked his son what is good for a person who is growing old, the answer came instantly: “good-natured children.” As we age, our relationship with our children changes, and its significance in our lives becomes more visible. Passing life on to them, speaking the same language, thinking, and sharing—this is also a way to stay current. The day comes when, instead of us teaching them, they begin to teach us. Especially in fast-moving fields like technology, some elders can’t keep pace without their children. Hence Schmid’s point: “Through our children, we can stay connected to the world.” But this bond remains healthy only if we avoid becoming a burden to our children.
Speaking of being a burden, let me be clear: a child caring for his father’s health, listening when he is down, and making time for him is not a burden. It is the natural extension of a healthy relationship built on mutual love and respect. The “burden” herein is something else: trying to fill our children’s lives with the gaps in our own, loading the consequences of our choices onto their shoulders, or expecting them to do what we can no longer do. Consequently, all these may, over time, upset the balance of the relationship. As some people age, their own needs sit so firmly at the center that they no longer see their children’s boundaries. However, growing old together requires recognizing and respecting those boundaries. The line between accepting help and becoming dependent is thin. Asking for support is one thing; handing over responsibility for your life is another. Let us not forget the difference.
And grandchildren? That bond is priceless—the very soul of my soul, as the saying goes. Especially if we can feel ourselves as a bridge between past and future, accept that with maturity, and smile, then the joy of time spent together is truly beyond words. Schmid notes that grandchildren inherit not only advice and stories from their grandparents, but also a sense of time. The bridge between then and now carries deep meaning for both the elderly and the young. Yet we must also mind the boundary: if we constantly judge the new world, aggressively question its order, and reject change, that bridge collapses quickly.
Not everyone is blessed with children or grandchildren. Yet Schmid argues that this is no obstacle. Being where children are, volunteering at a school, reading to them, even simply listening, can remind us that we still contribute to the world.
Jews have been stereotyped as self-interested traders, and some even compare the love of grandchildren to interest, seeing it as a pleasure without effort. I do not agree with this view. When I embrace my own grandchild, may God bless his path, I feel a delight I had never experienced before in this world. To me, the love of a grandchild is a fruit of paradise.
Even the bonds between siblings become more significant in old age. This is a closeness that begins in childhood and stretches across a lifetime. If you have someone with whom you can speak about anything, life becomes easier. Yet not every sibling relationship remains healthy. Schmid notes that long-standing resentments and inheritance disputes can strain ties. In such cases, staying calm becomes harder. Even so, in this stage of life, it is worth asking whether holding on to old grievances still serves any purpose.
My elder sister is my only sibling and my business partner. One of us was in the sixties, the other in the seventies; by now, I think we’ve learned what matters, and not to get caught up in details.
With cousins, nephews and nieces, and their spouses and children, we meet at certain times during the year. To feel you have relatives, and to see them, is a blessing. In our faith, it lengthens life.
The bond with the person with whom you share your life, grow old together, and build a new family, your spouse, deserves its own chapter. Schmid says: the vow to grow old together, made in youth, is now to be lived and honored. In old age, the form of the relationship changes. Togetherness demands greater understanding and more patience. When memory fades, movement slows, what came easily now requires effort, and the old allure is gone, it is calmness that protects respect and sustains love.
And of course, friendships. Retirement reduces workplace ties and narrows the social circle. But a friendship is one thing, a fellowship is quite another. Fellowship is not only about doing things together, but about truly being together. The kind of relationships where you can sit in silence, and after months apart, pick up exactly where you left off. With age, these friendships become even more valuable. Schmid adds, with a touch of humor but also depth, that many friendships are spared from many troubles precisely because they are not lived side by side. Not sharing the same home or the same routines means fewer fractures. A little distance can make a friendship stronger: expectations lessen, and the urge to settle scores fades. A true fellowship offers a closeness free of expectations.
I do not believe in retirement. I’ve lost count of how many times I’ve retired. May God protect us from infirmity. Our Holy Book, on this point, says: when tired of one task, find rest in another. (Surely, with hardship comes ease. Indeed, with hardship comes ease. So when you have finished one task, still strive hard, and to your Lord turn (all) your attention, Inshirah 5–8.) My first retirement was from the social security system at 40, and I didn’t feel it. Later, I retired from Ülker, when we acquired Godiva. Today I work at our global snacking company, pladis. In the future, I dream of building a digital business in a completely different category for global markets.
At times, we also look back on relationships that have fallen away. We sit with questions like: “Who is no longer in my life?” “Why did it end?” “If it happened today, would I still do the same?” Sometimes the answers come too late. If they don’t, perhaps a call is made, a short message is sent, and a path is found again.
If it is too late, then only how you carry that relationship in your mind remains. Not having offered a sincere apology, not having explained something, not even having said goodbye, all of these can linger in our minds. In such cases, we must make peace with the past on a mental plane, at least with the trace it has left on us. Perhaps even from what is too late, a measure of “calm” can still emerge.
I call up old acquaintances. I invite them to Friday prayers; if they come, we go together, and afterward we eat lunch in the cafeteria with everyone. On the way out, we give away books for free—so many are sent to me, in every kind and every language.
Finally, Schmid reminds us that enmity is also a form of relationship. As we age, we either let it go or learn to live at peace with it. Not everything must be forgiven, perhaps, but even enmity has its etiquette. You may even come to see that some enmities have taught you more than you realized. As Schmid puts it: “Does the enemy, through years of unwavering dedication to his role, not deserve a certain respect? Was it not the bitterness of anger and rage that helped us appreciate the sweetness of joy and love?” It gives you pause, doesn’t it?
CAN WE TRULY FORGIVE? I am not sure we can, for who can stop the world and turn it back one cycle? NO ONE. But was the wrong done to you personally, or to the system, to belief, and so on? Then leave the decision to those realms. I am not saying, “It’s none of your business”; I am asking what peace or benefit it will bring you. Are you chasing the gratification of ego? Or is it the fear of being humiliated?
JOY AND ENTERTAINMENT: Are we missing the kind of joy that lifts the spirit? Or is it just us, not noticing it, or not knowing how to enjoy it within what is permissible? I suggest reflecting on this. I once wrote a piece on our lives of entertainment and how we understand it. For those interested, here is the link: (https://muratulker.com/eglence-hayatimiz-anlayisimiz/).
Awareness and Calmness
According to Schmid, one of the paths to calmness is awareness. What once seemed complicated becomes simpler with age; its importance fades. As the final stage of life approaches, people begin asking themselves different questions: “Where did I come from?” “How did I live?” “If I had the chance, would I make the same choices again?” Asking such questions, seeking the answers, and making sense of our experiences is essential to understanding the meaning and value of life.
EMİR bi’L-MA’RÛF NEHİY ani’L-MÜNKER—what does it mean? To enjoin good and forbid evil. That, to me, is a lifelong duty: to spread what is good and prevent what is harmful. It is what sets me apart from all else, animate and inanimate, and it gives a profound sense of purpose.
THE PURPOSE OF MY LIFE: MAKE HAPPY, BE HAPPY
Today, we pay salaries to 80,000 people every month. But who can count how many families are touched by the global system we’ve built? Our manufacturing and sales operations cover countries with a combined population of 4 billion people, the very audience for our products. I am grateful, but let us be clear: motivating such a vast network, an ecosystem of this scale, and directing it toward goodness and beauty is no small task. The system I have found works everywhere, in every region, every language, every faith: MAKE HAPPY, BE HAPPY. We even celebrate it each year on the third Thursday of November as the “birthday” of our business, across the world, from the Far East to the Far West. Awareness, ownership, and participation are all remarkably high. And so, the philosophy on which we built our enterprise has been embraced and lived by our employees and stakeholders worldwide. Our mission is to spread goodness and beauty!
Our Approach to Death?!
With age, death becomes more real, more inevitable. We lose loved ones, we stand shoulder to shoulder at the funerals of fellows, we pray at their graves. We see clearly that our turn is drawing nearer. We begin to question how much time is left. Yet death remains a part of life.
Not everyone shares the idea of death as the destination. For many, it is less an ending than a passage. Life on this earth may conclude, but there is a belief that it continues elsewhere, in another form. This understanding points to the idea that what we do matters not only for its impact here, but also for its consequences on the other side. In this view, time is finite and precious, yet the whole story does not fit into this world alone. I am a man of faith, and for me, the meaning of life is not limited to the present moment. What matters is not only how I act, what I value, and whom I impact, but also my intent and my inner peace. As our Prophet said: All deeds are judged by their intentions.
At times, however, people must make decisions about their own death. Schmid says he personally would prefer to leave things to their natural course, though if circumstances became too difficult, he would not hesitate to allow intervention by his loved ones. Choices about death can take both active and passive forms: active euthanasia, the passive ending of life, or even suicide.
In my faith, all of these are considered haram, that is, religiously forbidden. The life God gives, only God can take. Still, we know there are those who choose these paths, or who consider them. Such decisions impact not only the individual but everyone around them. In the case of suicide, especially, those left behind may struggle to overcome questions like: “Was it because of me?” “Could I have done something about it?” Schmid acknowledges the seriousness of these issues and considers regulations like those in the Netherlands to be appropriate. Rules such as requiring repeated requests, confirmation of a terminal illness by multiple physicians, and execution by doctors only, he says, make the process sound both ethically and legally.
I could not disagree more. Let me tell you why. I was traveling in Africa, in Côte d’Ivoire, visiting a factory, when my phone rang. My wife was on the line from Istanbul, in tears: “They’re going to pull the plug on my father,” she said. My father-in-law had been in a serious accident and was in intensive care. I said, “No, wait. We’ll discuss it when I arrive.” And in time, my father-in-law left the hospital and spent a few truly joyful years with us. Even President Tayyip Erdoğan came to offer his good wishes, sharing a conversation with him.
I respect the author’s candor in addressing such difficult subjects. But I have not held back from sharing my own views, for in many ways I see things differently. After all, isn’t the very ability to feel gratitude toward a being we cannot name a profound sign of both the calm we possess and the power of that being?
References:
Wilhelm Schmid, Sakin Olmak: Yaşlanırken Kazandıklarımız, trans. Tanıl Bora, İletişim Publishing, 2024.
Note: This open-source article does not require copyright and can be quoted by citing the author.
