Nettle, D. (2005). Happiness: The science behind your smile. Oxford University Press.
Lua i Stíl Chicago (17ú heag.)Nettle, Daniel. Happiness: The Science Behind Your Smile. Oxford, UK ; New York, N.Y.: Oxford University Press, 2005.
Lua MLA (9ú heag.)Nettle, Daniel. Happiness: The Science Behind Your Smile. Oxford University Press, 2005.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.