I.G.Farbenind. Patent: US2198046 , 1937 ; Full Text Show Details I.G.Farbenind. Patent: DE728530 , 1936 ; DRP/DRBP Org.Chem. Full Text Show Details Newitt; Semerano Proceedings of the Royal Society of London, Series A: Mathematical, Physical and Engineering Sciences, 1936 , vol. 157, p. 354