1. ; ; : (to Soc. Edison), Ital. Pat. 682,880 (Febr. 19, 1965).
2. ; ; : (to Soc. Edison), U.S. Pat. 3,226,421 (Dec. 28, 1965).
3. ; : (to Soc. Edison), Ital. Pat. 749,678 (May 15, 1967).
4. ; : in Proceedings of the Fourth International Symposium on Heterogeneous Catalysis, Varna (Eds. ; ; ; ) Publ. House of the Bulgarian Academy of Sciences, Sofia, 1979, vol. II, p. 27.