1. R W Hay,Bioinorganic Chemistry, Ellis Harwood, Chichester, New York, 1984.
2. M N Hughes,The Inorganic Chemistry of Biological Process, John Wiley, Chichester, New York, 1988.
3. J M Pratt,Inorganic Chemistry of Vitamin B12, Academic Press, 1972.
4. G N Schrauzer, inAdvances in Chemistry series, No.100, Ed. R F Gould, American Chemical Society, Washington DC, 1971.