1. Agassiz, L., 1857, Embryology of the turtle. Contrib. Nat. Hist. USA 2: 451–644.
2. Amoroso, E.C., 1952, Placentation, in: “Marshall’s Physiology of Reproduction,” (A.S. Parkes, ed.), 3rd ed., Vol. II. pp. 127–311. Longmans, Green and Co., London.
3. Amoroso, E.C.and Perry, J.S., 1975, The existence during gestation of an immunological buffer zone at the interface between maternal and foetal tissues. Phil. Trans. Roy. Soc., Ser. B. 271: 343–361.
4. Bauchot, R., 1965, La placentation chez les reptiles. Ann. Biol. 4: 547–575.
5. Bellairs, R., 1971, Developmental Processes in Higher Vertebrates. Logos Press, London.