Helliwell, J. F., Layard, R., & Sachs, J. (2013). World happiness report 2013. Sustainable Development Solutions Network.
Citazione stile Chigago Style (17a edizione)Helliwell, John F., Richard Layard, e Jeffrey Sachs. World Happiness Report 2013. New York, N. Y: Sustainable Development Solutions Network, 2013.
Citatione MLA (9a ed.)Helliwell, John F., et al. World Happiness Report 2013. Sustainable Development Solutions Network, 2013.
Attenzione: Queste citazioni potrebbero non essere precise al 100%.