Napier, R. W., & Gershenfeld, M. K. (1989). Groups: Theory and experience (4th ed.). Houghton Mifflin.
Lua i Stíl Chicago (17ú heag.)Napier, Rodney W., agus Matti K. Gershenfeld. Groups: Theory and Experience. 4th ed. Boston: Houghton Mifflin, 1989.
Lua MLA (9ú heag.)Napier, Rodney W., agus Matti K. Gershenfeld. Groups: Theory and Experience. 4th ed. Houghton Mifflin, 1989.
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