(MONEY Magazine) – Apart from being linked in history, one thing the late Jacqueline Kennedy Onassis and Richard Nixon shared -- along with millions of Americans -- was the desire to die with dignity. News that both had signed so-called living wills prohibiting artificial life support may make you want to clarify your own wishes. If so, put them in writing, either through a living will or a lesser-known document called a durable power of attorney for health care. The basic difference between the two lies in whom you designate to make life-or- death decisions for you when you can't. With a living will, which covers only terminal patients, you give that power to your doctor by specifying in advance which treatments you want and don't want should you become fatally ill. For instance, you may okay cardiac resuscitation but not artificial breathing tubes. Under a durable power of attorney for health care, which also covers nonterminal cases such as comas, you appoint a trusted relative or friend who knows your wishes to tell the doctor how far to go in trying to keep you alive. Choice in Dying (800-989-9455), a right-to-die advocacy group, can send you the necessary forms for free and also advise you about the laws in your state. But remember to give the signed document to your doctor or your health-care proxy after you complete it. That piece of paper can buy great peace of mind -- but only if the right people know it exists.