1. Anonymous. (1921). The physiology of pain. The British Medical Journal, 1(3146), 571–572.
2. Aquinas, T. (1952). Summa theologica (Fathers of the English Dominican Province, Trans., and revised by D. J. Sullivan). Chicago, IL: Encyclopedia Britannica.
3. Aristotle. (1966). Ethica Nicomachea (W. D. Ross, Trans.). In W.D. Ross (Ed.), The works of Aristotle (Vol. IX of XII Vols. Set). London: Clarendon Press.
4. Aurelius, M. (1940). The meditations of Marcus Aurelius Antoninus (G. Long, Trans.). In W. J. Oates (Ed.), The stoic and epicurean philosophers: The complete and extant writings of Epicurus, Epictetus, Lucretius and Marcus Aurelius (pp. 491–587). New York: Random House.
5. Bain, A. (1892). Pleasure and pain. Mind (New Series), 1(2), 161–187.