1. Ackerman, R.A., Whittow. G.C.. Paganelli, C.V. and Pettit, T.N. (1980). Oxygen consumption, gas exchange, and growth of embryonic Wedge-tailed Shearwaters (Puffinus pacificus chlororhynchus). Physiol. Zool. 53: 210–221.
2. Barcroft, J., Flexner. L.B. and McClurkin. T. (1934). The output of the foetal heart in the goat. J. Physiol. (London) 82: 498–508.
3. Bohr, Chr. (1900). Der respiratorische Stoffwechsel des Säugethierembryo. Skand. Arch. Physiol.10: 413–424.
4. Carey, C., Thompson, E.L., Vleck, C.M. and James, F.C. (1982). Avian reproduction over an attitudinal gradient: incubation period. hatchling mass, and embryonic oxygen consumption. Auk99: 710–718.
5. Dawes. G.S. (1968). Foetal and Neonatal Physiology. Year Book, Chicago.