Kennon M. Sheldon and Sonja Lyubomirsky, «Achieving Sustainable Gains in Happiness: Change Your Actions, Not Your Circumstances», Journal of Happiness Studies 7 (2006): 55–86; Kennon M. Sheldon and Sonja Lyubomirsky, «Change Your Actions, Not Your Circumstances: An Experimental Test of the Sustainable Happiness Model», in Happiness, Economics, and Politics: Towards a Multi-disciplinary Approach, ed. Amitava Krishna Dutt and Benjamin Radcliff (Cheltenham, UK: Edward Elgar, 2009).
