1. American Society for Testing and Materials. 1970. Standard Method for Classification o Soils for Engineering Purposes. A.S.T.M. Designation: D. 2487–1969. Book of A.S.T.M. Standards, Part II 763–768. (American Society for Testing and Materials.)
2. British Standards Institution. 1957. Site Investigations. British Standard Code of Practice CP.2001. The Council for Codes of Practice, British Standards Institution.
3. British Standards Institution. 1967. British Standard 812: 1967. Methods for Sampling and Testing of Mineral Aggregates Sands and Fillers. London, British Standards Institution.
4. Classification of rocks for rock mechanics
5. Classification of rocks for rock mechanics