1. Lang, T. G. in Whales, Dolphins and Porpoise (ed. Norris, K. S.) 410–432 (University of California Press, Berkeley, 1966).
2. Hoerner, S. F. Fluid Dynamic Drag, 400 (Hoerner, S. R, Midland Park, New Jersey, 1965).
3. Hertel, H. Structure, Form and Movement, 251 (Reinhold, New York, 1966).
4. Webb, P. W. Bull. Fish. Res. Bd Can. 190, 158 (1975).
5. Weihs, D. J. mar. Res. 31, 195–209 (1973); J. theor. Biol. 48, 215–229 (1974).