1. J. H. Residorff, A. Haberkorn, M. Plempel and W. Stendel, German Offen. 2,533,605 (1977);
2. Chem. Abstr., 86, 171462g (1977).
3. G. Kleefeld, H. J. Diehr, W. Haas, H. W. Dehne and W. Brandes, German Offen. DE 4,033,412 (1992);
4. Chem. Abstr., 117, 42727g (1992).