1. R. M. Paton, in A. R. Katritzky and C. W. Rees (editors),Comprehensive Heterocyclic Chemistry, Vol. 6, Oxford (1984), p. 425.
2. R. Bohm and C. Karov,Pharmazic,4, 243 (1981).
3. G. Bertolini, C. Casagrande, and F. Santanglo, Eur. Patent 8922768;Chem. Abs.,115, 159145, (1991).
4. B. Loubinoux, J.-L. Colin, and S. Tabbache,J. Heterocycl. Chem.,21, 1669 (1984).
5. K. T. Finley in A. Weissberger and E. C. Taylor (editors),Chemistry of Heterocyclic Compounds, Vol. 39, Wiley, New York (1980), p. 1.