1923. KOPPERS, H., G. m. b. H. [Continuous Generation of Water Gas Free of Hydrocarbons From Bituminous Fuels.] German Patent 717,247, Jan. 22, 1942 (Cl. 24 c-1.05). Chem. Abs., vol. 38, 1944, pp. 2479-2480.

See United States Patent 2,148,299 (abs. 1919).