1. Bjerrum (1915). Ugesk. f Laeger. Kbenh., 77, 407.
2. Bonnet, A. (1930). Thesis, Paris.
3. Commandeur, M. (1904). Bull. de la Soc. d'Obstet de Paris, 7, 54.
4. Personal communication;Cranwell, D.J.;Rev. Gynec. et de' Chir. abd,1905
5. Mahoney, P. I., and Chamberlain, J. W. (1940). J. Pediat., 17, 772.