Cita APA (7a ed.)

Campbell, M. W., & Waal, F. B. M. d. (2011). Ingroup-outgroup bias in contagious yawning by chimpanzees supports link to empathy. Public Library of Science (PLoS).

Cita Chicago Style (17a ed.)

Campbell, Matthew W., y Frans B M de Waal. Ingroup-outgroup Bias in Contagious Yawning by Chimpanzees Supports Link to Empathy. Public Library of Science (PLoS), 2011.

Cita MLA (8a ed.)

Campbell, Matthew W., y Frans B M de Waal. Ingroup-outgroup Bias in Contagious Yawning by Chimpanzees Supports Link to Empathy. Public Library of Science (PLoS), 2011.