1. Van Duuren, B. L. Progr. exp. Tumor Res. 11, 31–68 (1969).
2. Hecker, E. Methods Cancer Res. 6, 439–484 (1971).
3. Boutwell, R. K., C.R.C. Crit. Rev. Toxic. 2, 419–443 (1974).
4. Weinstein, I. B., Wigler, N. & Pietropaolo, C. in Cold Spring Harbor Symposium on the Origins of Human Cancer (Cold Spring Harbor Laboratory, Cold Spring Harbor, New York, in the press).
5. Cohen, R., Pacïfici, M., Rubinstein, N., Biehl, J. & Holtzer, H. Nature 266, 538–540 (1977).