1. Barenbers, Greene, Greenspan: The Journal of Pediatrics, Vol. 18, 1941, p. 579.
2. Brennemanna’ Practice of Pediatrics, 1945, Vol. 3, Chapter 7, p. 10.
3. Bruening: 49. Tagung der Deutschen Gesellschaft fuer Chirurgie, 1925.
4. Court and Halser: ref. Amer. Jour. Dis. of Chil., Vol. 66, 1943, p. 674.
5. De Takats and Biggs: Jour. Pediat., Vol. 13, 1938, p. 819.