Seligman, M. E., & Csikszentmihalyi, M. (2000). Positive psychology. An introduction. The American psychologist, 55 (1), 5-14. https://doi.org/10.1037/0003-066X.55.1.5
Reker.G.T. &Wong, P. T. P. (2012). Personal meaning in life and psychosocial adaptation in the later years. In Wong, P. T. P. (Ed.). (2012). The human quest for meaning: Theories, research, and applications (2nd ed.). Routledge/Taylor & Francis Group.pp.433-456