1. F. Feigl, Spot Tests in Organic Analysis. New York: Elsevier. 1966.
2. F. J. Welcher, Organic Analytical Reagents, Vol. II to IV. New York: Van Nostrand. 1955.
3. F. D. Snell andC. T. Snell, Colorimetric Methods of Analysis, Vol. II. New York: Van Nostrand. 1951.
4. L. Meites, Handbook of Analytical Chemistry. London: McGraw Hill Book Co. 1963. p. 6–53.
5. H. B. Mark, L. M. Backer, D. Pinkel, andL. J. Papa, Talanta12, 27 (1965).