1. S. Johne and D. Groeger, Pharmazie, 25, 22 – 44 (1970).
2. S. Johne, Pharmazie, 36, 583 – 596 (1981).
3. J. B. Hynes and W. T. Ashton, J. Med. Chem., 18, 263 – 265 (1975).
4. E. T. Elslager, P. Jacob, J. Johnson, and L. M. Werbel, J. Heterocycl. Chem., 17, 129 – 136 (1980).
5. I. P. Tregubenko, B. V. Golomolzin, I. Ya. Postovskii, et al., in: Organic Synthesis and Biological Activity [in Russian], Sverdlovsk (1978), pp. 3 – 13.