1. T. Godfraid, R. Miller, M. Wibo, Pharmocol. Rev. 38, 321 (1986)
2. A. Sausins, G. Duburs, Heterocycles 27, 279 (1988)
3. P.P. Mager, R.A. Coburn, A.J. Solo, D.J. Triggle, H. Rothe, Drug Des. Discov. 28, 273 (1992)
4. R. Mannhold, B. Jablonka, W. Voigt, K. Schonafinger, K. Schraven, Eur. J. Med. Chem. 27, 229 (1992)
5. F. Bossert, H. Meyer, E. Wehinger, Angew. Chem. Int. Ed. Engl. 20, 762 (1981)