Lyn H. (2007) Mental representation of symbols as revealed by vocabulary errors in two bonobos (Pan paniscus). Animal Cognition 10:461–75.
Lyn H., Greenfield P. M. & Savage-Rumbaugh E. S. (2006) The development of representational play in chimpanzees and bonobos: Evolutionary implications, pretense, and the role of interspecies communication. Cognitive Development 21:199–213.
Lyn H. & Savage-Rumbaugh E. S. (2000) Observational word learning by two bonobos: Ostensive and non-ostensive contexts. Language and Communication 20:255–73.
Rumbaugh D. M., King J. E., Beran M. J., Washburn D. A. & Gould K. L. (2007) A salience theory on learning and behavior: With perspectives on neurobiology and cognition. International Journal of Primatology 28:973–96.
Rumbaugh D. M. & Washburn D. A. (2003) The intelligence of apes and other rational beings. Yale University Press.
Savage-Rumbaugh E. S., McDonald K., Sevcik R. A., Hopkins W. D. & Rupert E. (1986) Spontaneous symbol acquisition and communicative use by pygmy chimpanzees (Pan paniscus). Journal of Experimental Psychology: General 115:211–35.