1. P. E. Browning andP. L. Blumenthal, seeF. A. Gooch, Methods in Chemical Analysis, 1st edition. New York: Wiley. 1912. p. 160.
2. A. J. Mee, A New Scheme of Elementary Qualitative Analysis. London: Dent. 1942. pp. 11, 24.
3. H. Holness, Advanced Inorganic Qualitative Analysis. London: Pitman. 1957. p. 63.