1. Cairns, H. (1942). Lisboa med., 19, 375.
2. Caldwell, J. A. (1936). Amer. J. Surg., 32, 522.
3. Cloake, P. C. P. (1951). In Modern Trends in Neurology, p. 466, ed. A.
4. Connolly, C. (1954). Soc. Brit. Neurol. Surg., Belfast. Discussion.
5. Davis, L., and Perret, G. (1947). Brit. J. Surg., 34, 307.