1. C. B�deker, Ann. Chem.117, 193 (1861).
2. F. Feigl, Spot Tests in Inorganic Analysis, 5th Engl. Ed., Amsterdam: Elsvier. 1958. pp. 307?309.
3. G. Scagliarini, Atti acad. Lincei22, 155 (1935).
4. W. Moser, R. A. Chalmers, and A. G. Fogg, J. Inorg. Nucl. Chem.27, 831 (1965).
5. A. G. Fogg, A. H. Norbury, and W. Moser, J. Inorg. Nucl. Chem.28, 2735 (1966).