Trahan, M., & Gray, P. (1991). Focus on psychology: A guide to mastering Peter Gray's psychology. Worth.
Lua i Stíl Chicago (17ú heag.)Trahan, Mary, agus Peter Gray. Focus on Psychology: A Guide to Mastering Peter Gray's Psychology. New York: Worth, 1991.
Lua MLA (9ú heag.)Trahan, Mary, agus Peter Gray. Focus on Psychology: A Guide to Mastering Peter Gray's Psychology. Worth, 1991.
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