Rediscovering the Later Version of Maslow’s Hierarchy of Needs: Self-Transcendence and Opportunities for Theory, Research, and Unification.
Koltko-Rivera, Mark E. “Rediscovering the Later Version of Maslow’s Hierarchy of Needs: Self-Transcendence and Opportunities for Theory, Research, and Unification.” Review of General Psychology, vol. 10, no. 4, 1 Dec. 2006, pp. 302–317., doi:10.1037/1089-2680.10.4.302. [https://www.simplypsychology.org/maslow(2).pdf].