Sheldon KM and Elliot AJ: Goal Striving, Need Satisfaction, and Longitudinal Well-being: The Self-concordance model, Journal of personality and Social Psychology, 76(3) 482-497, 1999
Sheldon KM and Houser L: Self-concordance, Goal attainment, and the pursuit of happiness: Can there be an upward Spiral? Journal of personality and social psychology 80(1) 152-165, 2001