R. D. M.  Page, ?On describing the shape of rooted and unrooted trees?, Cladistics, vol. 9, pp. 93?99, 1993.

R. D. M.  Page, ?NDE (NEXUS Data Editor for Windows)?. Published by the author, Glasgow, United Kingdom, 2001.

R. D. M.  Page and Holmes, E. C., Molecular evolution: a phylogenetic approach. Oxford: Wiley-Blackwell, 1998, p. 346.