1. Properties of laterites from Ilorin, Nigeria;Alao,1982
2. Procedures for Testing Soils;A.S.T.M. (American Society for Testing Materials),1964
3. Clay minerals: A guide to their X-ray identification;Carroll;Geol. Soc. Am. Spec. Pap.,1970
4. Values for international geochemical reference standards;Flanagan;Geochim. Cosmochim. Acta,1973