Bilhuber Inc. Patent: AT134561 ; Full Text Show Details Bilhuber Inc. Patent: US1972450 , 1931 ; Full Text Show Details Knoll A.G. Patent: CH163535 , 1932 ; Full Text Show Details Knoll A.G. Patent: DE617536 , 1931 ; Fortschr. Teerfarbenfabr. Verw. Industriezweige, vol. 21, p. 680,682 Full Text Show Details Knoll A.G. Patent: DE617879 , 1932 ;