1. 1) W. R. MADDOCKS and E. T. TURKDOGAN : JISI, 168 (1949), p. 249
2. 2) W. R. MADDOCKS and E. T. TURKDOGAN : JISI, 171 (1952), p. 128
3. 3) W. OELSEN : Arch. Eisenhuttenw., 36 (1965), p. 861
4. 13) J. W. MELLOR : A Comprehensive Treatise on Inorganic and Theoretical Chemistry II (1956), p. 1143 [Longmans, Green and CO.].
5. 14) A. E. NEWWKIRK and I. ALLIFERIS : Analy. Chem., 30 (1958), p. 982