1. E. HAYEK and W. STADLMANN,Angew. Chem. 67 (1955) 327.
2. S. V. CHIRANJIVI RAO and N. S. CHICKERUR,Indian J. Chem. 12 (1974) 523.
3. S. V. CHIRANJIVI RAO,J. Indian Chem. Soc. 53 (1976) 352.
4. F. J. WELCHER, ?The analytical uses of ethylenediamine tetraacetic acid? (Van Nostrand, Princeton, New Jersey, 1965).
5. J. R. PARTINGTON, in ?An advanced treatise on physical chemistry?, Vol. 3 (Longmans Green, New York, 1952) p. 121.