Hi Daniel,
How about the following publication? The text is available online if your library subscribes, try http://www.sciencedirect.com/science/journal/00255564
Swofford, D. L., and Maddison, W. P. (1987). Reconstructing Ancestral Character States Under Wagner Parsimony. Mathematical Biosciences 87, 199-229.
(Nur am Rande, Du bekommst womoeglich besseres feed-back, wenn Du auf Englisch fragst.)
Gruss,
Julia
