Brosnan, S. F., Silk, J. B., Henrich, J., Mareno, M. C., Lambeth, S. P., & Schapiro, S. J. (2009). Chimpanzees (Pan troglodytes) do not develop contingent reciprocity in an experimental task. Springer-Verlag.

Brosnan, Sarah Frances, Joan B. Silk, Joseph Henrich, Mary Catherine Mareno, Susan P. Lambeth, ja Steven J. Schapiro. Chimpanzees (Pan Troglodytes) Do Not Develop Contingent Reciprocity in an Experimental Task. Springer-Verlag, 2009.

Brosnan, Sarah Frances, et al. Chimpanzees (Pan Troglodytes) Do Not Develop Contingent Reciprocity in an Experimental Task. Springer-Verlag, 2009.