1. Beischer, N.A. and MacKay, E.V. (1978): Obstetrics and the Newborn. Saunders Ltd., East Sussex.
2. Burtis, C.A. and Ashwood, E.R. (1994): Clinical chemistry of pregnancy. In Tietz Textbook Clinical Chemistry, 2nd ed, (Burtis, C.A. and Ashwood, E.R., eds.), pp.2107-2148, WB Saunders Company, Philadelphia.
3. Challis, J.R.G., Davies, I.J. and Ryan, K.J. (1973): The concentrations of progesterone, estrone and estradiol-17β in the plasma of pregnant rabbits. Endocrinology, 93, 971-976.
4. Pregnancy Dating in the Rat: Placental Morphology and Maternal Blood Parameters
5. Howells, M., Jones, S., Napier, A., Saunders, K. and Cavill, I. (1986): Erythropoiesis in pregnancy. Br. J. Haematol., 64, 595-599.