Glossary of "Cladistics (2nd ed.)" by Kitching et al. (1998)
- A method of character polarization that states that the character state found in the taxon furthest geographically or ecologically from the ancestral taxon is apomorphic. Also known as the criterion of chorological progression.
- Kitching, I. J., Forey, P. L. Humphries, C. J. & Williams, D. M. 1998. Cladistics, 2nd ed.: the Theory and Practice of Parsimony Analysis. -xii + 228 pp. Oxford University Press, New York.