Millová, Katarína, and Marek Blatný. 2015. "Personality Development: Systems Theories" Pp. 879–83 in International Encyclopedia of the Social & Behavioral Sciences (2nd ed.). doi:10.1016/B978-0-08-097086-8.23035-3.
Hodapp, Robert M. 1999. "Indirect Effects of Genetic Mental Retardation Disorders: Theoretical and Methodological Issues." International Review of Research in Mental Retardation 22:27–50. doi:10.1016/S0074-7750(08)60130-5