1. L. M. Bershtein, Vopr. Onkol., No. 8, 87 (1982).
2. V. M. Dil'man, Endocrinologic Oncology [in Russian], Leningrad (1983).
3. T. S. Saatov, Ukr. Biokhim. Zh., No. 2, 44 (1981).
4. V. A. Tkachuk and G. N. Baldenkov, Biokhimiya, No. 6, 1097 (1978).
5. N. A. Fedorov, Biological and Clinical Importance of Cyclic Nucleotides [in Russian], Moscow (1979).