1. Renfree, M.B., In Lamming, G.E. (eds.) Marshall’s Physiology of Reproduction (vol.3. edn.), Chapman 0000 Hall, London, 1994, p. 677.
2. Renfree, M.B., Green, S.W. and Young, I.R., J. Reprod. Fert., 57 (1979) 131.
3. Harder, J.D., Hinds, L.A., Horn, C.A. and Tyndale-Biscoe, C.H., J. Reprod. Fert., 75 (1985) 449.
4. Tyndale-Biscoe, C.H., J. Reprod. Fert., 19 (1969) 1191.
5. Krause, W.J., Zool. Anz. 230 (1993) 249: