1. Allison, S.T., G.R. Goethals, A.R. Marrinan, O.M. Parker, S.P. Spyrou, and M. Stein. 2019. The metamorphosis of the hero: Principles, processes, and purpose. Frontiers in Psychology 10: 606.
2. Beck, D.E., and C.C. Cowan. 2005. Spiral dynamics: Mastering values, leadership and change. New York: Wiley.
3. Boehm, B.W. 1989. Software risk management. Piscatawy: IEEE Computer Society Press.
4. Brendtro, L.K., M. Brokenleg, and S. Van Bockern. 2005. The circle of courage and positive psychology. Reclaiming Children and Youth 14: 130–136.
5. Campbell, J. 1949. The hero with a thousand faces. New York: New World Library.