1. Beinert H, Holm RH, Munck E (1997) Iron-sulfur clusters. Nature’s modular, multipurpose structures. Science 277:653–659
2. Birch NJ (1993) Magnesium and the cell. Academic Press, London
3. Carafoli E, Klee C (eds) (1999) Calcium as a cellular regulator. Oxford Univ. Press, New York
4. Fraústo da Silva JJR, Williams RJP (2001) The biological chemistry of the elements. Oxford University Press, Oxford
5. Hill HAO, Sadler PJ, Thomson AJ (1998) Metal sites in proteins and models. Structure and bonding vols 88, 89 and 90