1. Durrant PJ, Durrant B (1962) Introduction to advanced inorganic chemistry. Longmans, London
2. Wells AF (1962) Structural inorganic chemistry. 3rd edn. Oxford University Press, London
3. Schmidt M, Siebert W (1973) Sulphur. In: Trotman-Dickenson AF (ed.) Comprehensive Inorganic Chemistry (Vol 2), Pergamon Press, Oxford
4. Bagnall KW (1973) Selenium, tellurium and polonium. In: Trotman-Dickenson AF (ed.) Comprehensive inorganic chemistry (Vol 2), Pergamon Press, Oxford
5. Greenwood NN, Earnshaw A (1984) Chemistry of the elements. Pergamon Press, Oxford.