1. Physical versus social scarcity of minerals
2. (As adopted by the Nomenclature Committee for International Mineralogical Association), Grim, R. E.Clay Mineralogy, p. 34, McGraw-Hill Book Co., 2nd edn, London (1968).
3. Thomas, D., Pillai, P. K., Mukundan, P. and Patel, M. (unpublished data).