1. Australian Patent No. 156,396 (1954).
2. Swiss Patent No. 292,943 (1953).
3. British Patent No. 700,677 (1953).
4. L. F. Larionov, in: Problems of Chemistry in Oncology [in Russian], Leningrad (1968), pp. 64–86.
5. L. D. Bergel'son, Zh. Vses. Khim. Ova., No. 3, 322–342 (1975).