1. Roth, G. & Wullimann, M. F. in Neurowissenschaft: vom Molekül zur Kognition (eds Dudel, J., Menzel, R. & Schmidt, R. F.) 1–31 (Springer, Berlin, 1996). This is a well illustrated, balanced review of nervous system evolution throughout the animal kingdom (although the information is presented in the context of an out-of-date cladogram).
2. Allman, H. Evolving Brains (Scientific American Library, New York, 1999).
3. Wullimann, M. F. in Brain Evolution and Cognition (eds Roth, G. & Wulliman, M. F.) 11–40 (Wiley, New York, 2001).
4. Northcutt, R. G. Understanding vertebrate brain evolution. Integ. Comp. Biol. 42, 743–756 (2002).
5. Bullock, T. H. Grades in neural complexity: how large is the span? Integ. Comp. Biol. 42, 757–761 (2002).