Species of marine invertebrates: a comparison of the biological and phylogenetic species conceptsChapman and Hall199–219
Knowlton, Nancy and Weigt, Lee A. 1997. "Species of marine invertebrates: a comparison of the biological and phylogenetic species concepts." In Species: the Units of Biodiversity, Systematics Association (UK) Special Volume Series 54. Claridge, M. F., Dawah, H. A., and Wilson, M. R., editors. 199–219. Chapman and Hall.