1. Buckley, J. D., O'Connor, P. J. & Craig, A. W. Nature 281, 403–404 (1979).
2. Teebor, G. W. & Becker, F. F. Cancer Res. 31, 1–3 (1971).
3. Epstein, S., Ito, N., Merkow, L. & Farber, E. Cancer Res. 27, 1702–1711 (1967).
4. Scuidero, D., Norin, A., Karran, P. & Strauss, B. Cancer Res. 36, 1397–1403 (1976).
5. Sirover, M. A. Cancer Res. 39, 2090–2095 (1979).