1. F. E. Beamish, The Analytical Chemistry of the Noble Metals, Oxford: Pergamon. 1966. p. 418.
2. G. H. Ayres and Q. Quick, Analyt. Chemistry22, 1403 (1950).
3. G. H. Ayres and W. T. Bolleter, Analyt. Chemistry29, 72 (1957).
4. H. Robinson, Engelhard Ind., Tech. Bull.4, 91 (1963).
5. V. N. Danilova and S. L. Lisichenok, Zavod. Lab.34, 1284 (1968).