I.G. Farbenind. Patent: DE579323 , 1932 ; Fortschr. Teerfarbenfabr. Verw. Industriezweige, vol. 20, p. 1328 Full Text Show Details Gen. Aniline Works Patent: US1975386 , 1933 ; Full Text Show Details Du Pont de Nemours and Co. Patent: US2795593 , 1953 ;