Schroeder, D. A., & Penner, L. A. (1995). The psychology of helping and altruism: Problems and puzzles. McGraw-Hill.
Lua i Stíl Chicago (17ú heag.)Schroeder, David A., agus Louis A. Penner. The Psychology of Helping and Altruism: Problems and Puzzles. New York: McGraw-Hill, 1995.
Lua MLA (9ú heag.)Schroeder, David A., agus Louis A. Penner. The Psychology of Helping and Altruism: Problems and Puzzles. McGraw-Hill, 1995.
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