(1955). Keys to happiness: A Reader's Digest guide to successful living. The Reader's Digest Association.
Chicago-referens (17:e uppl.)Keys to Happiness: A Reader's Digest Guide to Successful Living. The Reader's Digest Association, 1955.
MLA-referens (9:e uppl.)Keys to Happiness: A Reader's Digest Guide to Successful Living. The Reader's Digest Association, 1955.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.