1. J. Elguero , C.Marzin, A. R.Katritzky and P.Linda, The Tautomerism of Heterocycles, Academic Press, New York, 1976, pp. 339et seq.;
2. J. Elguero , C.Marzin, A. R.Katritzky and P.Linda, The Tautonterism of Heterocycles, Academic Press, New York, 1976, p. 20;
3. J. Elguero , C.Marzin, A. R.Katritzky and P.Linda, The Tautonterism of Heterocycles, Academic Press, New York, 1976, p. 352;
4. J. Elguero , C.Marzin, A. R.Katritzky and P.Linda, The Tautonterism of Heterocycles, Academic Press, New York, 1976, p.124;
5. J. Elguero , C.Marzin, A. R.Katritzky and P.Linda, The Tautonterism of Heterocycles, Academic Press, New York, 1976, p. 291;