1. Berrill, N. J., Karp, G.: Development. New York: McGraw-Hill 1976
2. Bordzilovskaya, N. P., Dettlaff, T. A.: Axolotl Newsletter 7, 2 (1979)
3. Chibon, P.: J. Embryol. exp. Morph. 18, 343 (1967)
4. Ciment, G., Weston, J. A.: Dev. Biol. 93, 355 (1982)
5. Dalton, H. C.: J. Exp. Zool. 115, 17 (1950)