(1955). Keys to happiness: A Reader's Digest guide to successful living. The Reader's Digest Association.
Citazione stile Chigago Style (17a edizione)Keys to Happiness: A Reader's Digest Guide to Successful Living. The Reader's Digest Association, 1955.
Citatione MLA (9a ed.)Keys to Happiness: A Reader's Digest Guide to Successful Living. The Reader's Digest Association, 1955.
Attenzione: Queste citazioni potrebbero non essere precise al 100%.