Zahn-Waxler, Carolyn, and Carol Van Hulle. "Empathy, Guilt, and Depression: When Caring for Others Becomes Costly to Children." Pathological Altruism. : Oxford University Press, 2011-12-09. Oxford Scholarship Online. 2012-01-19. Date Accessed 25 May. 2013 <http://www.oxfordscholarship.com/view/10.1093/acprof:oso/9780199738571.001.0001/acprof-9780199738571-chapter-025>.
Zahn-Waxler, C., & Van Hulle, C.(2011-12-09). Empathy, Guilt, and Depression: When Caring for Others Becomes Costly to Children. In Pathological Altruism. : Oxford University Press. Retrieved 25 May. 2013, from http://www.oxfordscholarship.com/view/10.1093/acprof:oso/9780199738571.001.0001/acprof-9780199738571-chapter-025.
Zahn-Waxler, Carolyn, and Carol Van Hulle. "Empathy, Guilt, and Depression: When Caring for Others Becomes Costly to Children." In Pathological Altruism. : Oxford University Press, 2011-12-09. http://www.oxfordscholarship.com/view/10.1093/acprof:oso/9780199738571.001.0001/acprof-9780199738571-chapter-025.
Zahn-Waxler C, Van Hulle C. Empathy, Guilt, and Depression: When Caring for Others Becomes Costly to Children. In: Oakley B, Knafo A, Madhavan G, Wilson DS. Pathological Altruism. Oxford University Press; 2011. http://www.oxfordscholarship.com/view/10.1093/acprof:oso/9780199738571.001.0001/acprof-9780199738571-chapter-025. Accessed May 25, 2013.