Gaya APA

Schroeder, D, A. et al (1995). The psychology of helping and altruism: problem and puzzles . United States of America: Mc Graw Hill, Inc.

Gaya MLA

Schroeder, David, A.. et al. "The psychology of helping and altruism: problem and puzzles". United States of America: Mc Graw Hill, Inc, 1995. Text.