1. Dalbert, P., Bulletin Assoc. Franc. Etude Cancer 5, Page 121, 1912.
2. Walker, C. H. and Klein, F., American Medicine, Page 628, 1915.
3. Todd, A. T., British Medical Journal, Page 172, 1935.
4. Nelson, A. A., Fitzhugh, O. G. and Calvery, H. O., Cancer Research 3, Page 230, 1943.
5. Tscherkes, L. A., Volgarev, N. M. and Aptekar, S. G., Acta Uv Int. Cancer 19, Page 632, 1963.