1. ASTM D698 (2012). Standard test methods for laboratory compaction characteristics of soil using standard effort (12,400 ft-lbf/ft3 (600 kN-m/m3)).
2. ASTM D1557 (2012). Standard test methods for laboratory compaction characteristics of soil using modified effort (56,000 ft-lbf/ft3 (2,700 kN-m/m3)).
3. Blotez, L., Benson, C., and Boutwell, G. (1998). “Estimating optimum water content and maximum dry unit weight for compacted clays.” J. Geotech. Engrg., ACSE, Vol. 124, No. 9, pp. 907–912, DOI: 10.1061/(ASCE)1090-0241(1998)124:9(907) .
4. Boutwell, G. (1961). Effects of variation of fill construction on the material properties and the subsequent fill performance, Independent Study Rep., School of Civ. Engrg., Georgia Institute of Technology, Atlanta, Ga.
5. Grim, R. E. and Cuthbert, F. L. (1945). “Some claywater properties of certain clay minerals.” Journal of the American Ceramic Society, Vol. 28, No. 3, pp. 90–95, DOI: 10.1111/j.1151-2916.1945.tb14518.x .