Oxford scholarship online (Online service), Emmons, R. A., & McCullough, M. E. (2004). The psychology of gratitude. Oxford University Press. https://doi.org/10.1093/acprof:oso/9780195150100.001.0001
Cita Chicago (17th ed.)Oxford scholarship online (Online service), Robert A. Emmons, i Michael E. McCullough. The Psychology of Gratitude. Oxford: Oxford University Press, 2004. https://doi.org/10.1093/acprof:oso/9780195150100.001.0001.
Cita MLA (9th ed.)Oxford scholarship online (Online service), et al. The Psychology of Gratitude. Oxford University Press, 2004. https://doi.org/10.1093/acprof:oso/9780195150100.001.0001.
Atenció: Aquestes cites poden no estar 100% correctes.