BASF Aktiengesellschaft
Patent: US4761489 A1, 1988 ;

Abuzov, B. A.; Klimovitskii, E. N.; Remizov, A. B.; Timirbaev, M. B.
Bulletin of the Academy of Sciences of the USSR, Division of Chemical Science (English Translation), 1981 , vol. 30, # 5 p. 794 - 799
Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, 1981 , # 5 p. 1030 - 1036