1. P. Buehlmayer, and P. Furet, Ciba Geigy A, PCT Int. Appl. WO 94 13,651 (1994);
2. Chem. Abstr., 122, 214113a (1995).
3. J. F. F. Liegeois, and J. E. Delarge, Therabel Research S.A./N.V, U.S., US Patent 5,393,752 (1995);
4. Chem. Abstr., 123, 83396r (1995).
5. D. W. Hansen, and K. B. Peterson, G. D. Searle and Co., PCT Int. Appl. WO 94 29, 286 (1994);