1. Contact Mechanics;Johnson,1985
2. A sensitive pyramidal-diamond toll for indentation measurements;Knoop;J Res Nat Bur Stand,1939
3. ASTM C1326-96a Standard Test Method for Knoop Indentation Hardness of Advanced Ceramics.
4. Axially symmetric plastic deformations in soils;Cox,1961
5. Limit analysis and Soil Plasticity;Chen,1975