1) Yamagiwa, K., and Ichikawa, K.(1915) Experimentelle studie uber die pathogenese der epithelialgeschwulste. Mitt. Med. Fad. Tokio, 15: 295-344
2) Kennaway, E. L.(1930) Further experiments on cancer producing substances, Biochem. J., 24: 497-504
3) Cook, J. W., Hewett, C. L., and Hieger, I.(1933): The isolation of a cancer-producing hydrocarbon from coal tar-Parts I, H and HI. J. Chew. Soc., Transactions, 1: 395-405
4) Waller, R. E.(1952) The benzo (a) pyrene content of town air, Brit. J. Cancer, 8: 8-21