1. Lamarck, J. B. Philosophie Zoologique [in French] Vol. 2 (Dentu, 1809). The first explicitly evolutionary derivation of vertebrates from invertebrates.
2. Geoffroy St-Hilaire, E. Considérations générales sur la vertèbre [in French]. Mém. Mus. Hist. Nat. 9, 89–119 (1822).
3. Patten, W. The Evolution of the Vertebrates and Their Kin (Blakiston's Son, 1912).
4. Gislén, T. Affinities between the Echinodermata, Enteropneusta, and Chordania. Zool. Bidr. Uppsala 12, 199–304 (1930).
5. Jefferies, R. P. S. The Ancestry of the Vertebrates (British Museum Natural History, 1986). This scholarly work, even if no longer accepted in its broad outline, was centrally important for reawakening interest in the invertebrate-to-vertebrate transition in the latter part of the twentieth century.