1. T. Hata, Y. Sano, R. Sugawara, A. Matsumae, K. Kanamori, T. Shima and T. Hoshi, J. Antibiot, (Japan) Ser. A9 (1956) 14.
2. S.T. Crooke, in Cancer Chemotherapy, Vol. 3, eds. S.T. Crooke and A.W. Prestayko, Academic Press, New York (1981) p. 49.
3. V.N. Iyer and W. Szybalski, Science 145 (1964) 55.
4. Earlier reviews: (a) W.A. Remers, in The Chemistry of Antitumor Antibotics, Vol. 1, Wiley, New York (1979) Chap. 5
5. R.W. Franck, Prog. Chem. Org. Natl. Prod. 38 (1979) 1.