Nielsen, C. 1997. Animal classification - then and now. Nielsen, C. 1998. Origin and evolution of animal life cycles. Nielsen, C. 1998.
Sequences lead to trees of worms.
Nielsen, C. 1998. Morphological approaches to phylogeny. Nielsen, C. 1999. Origin of the chordate central nervous system - and the origin of the chordates. Nielsen, C. 1999.