1. Tatchell, J. A. H., 190, 837 (1961).
2. Heston, W. E., J. Nat. Cancer Inst., 3, 69, 79 (1942).
3. Heston, W. E., J. Nat. Cancer Inst., 2, 127 (1941).
4. Heston, W. E., Deringer, M. K., Hughes, I. R., and Cornfield, J., J. Nat. Cancer Inst., 12, 1141 (1952).
5. Heston, W. E., Nature, 172, 1007 (1953).