Educational psychology: A contemporary view.Del Mar, CA: C.R.M., 1973.
5.
LepperM. R.GreeneD.NisbettR.Undermining children's intrinsic interest with extrinsic reward: A test of the “overjustification” hypothesis. Journal of Personality and Social Psychology, 1973, 28, 129–137.
6.
MaehrM. L.Continuing motivation: An analysis of a seldom considered educational outcome. Review of Educational Research, 1976, 46, 443–462.
7.
StawB. M.Intrinsic and extrinsic motivation. University Programs Modular Series. Morristown, NJ: General Learning Press, 1976.