1. Goldman, F. H., u. H. Gagoda: Ind. Eng. Chem. Anal. Bd.15 (1934) S. 377/378.
2. Romijn, G.: Z. analyt. Chem. Bd.36 (1897) S. 19.
3. Jacobs, M. B.: Analytical Chemistry of Industrial Poisons, Hazards and Solvents. New York 1941: Interscience Publishers.