Early Tetrapod
Links
Clack, J.
http://www.zoo.cam.ac.uk/zoostaff/clack.htm
Early tetrapod evolution (Univ. Cambridge, Mus. of Zoology).
Laurin, M.
http://tolweb.org/tree/laurin/Laurin_Home_page.html
The origin and phylogeny of tetrapods (Université Paris).