Layard, P. R. G. (2005). Happiness: Lessons from a new science. Penguin Press.
Chicago Style aipamenaLayard, P. R. G. Happiness: Lessons from a New Science. New York: Penguin Press, 2005.
MLA aipamenaLayard, P. R. G. Happiness: Lessons from a New Science. Penguin Press, 2005.
Kontuz: berrikusi erreferentzia hauek erabili aurretik.