13. Groups today are not closed systems
in Muzafer and Carolyn Wood Sherif Papers, of University of Akron. Cummings Center for the History of Psychology; with Muzafer Sherif, 1906-1988, Series 5: Research Studies, 1949-1967, Sub-series 2: Robber's Cave Study, 1953-1954, Box M3552, Folder 1 , 24 page(s)