1. American Society for Testing and Materials 1995 ASTM standard D5778-95. Standard test method for performing electric friction cone and piezocone penetration testing of soils 576 In Annual book of ASTM standards West Conshohocken, PA
2. A new hand-held recording penetrometer for soil studies;Anderson;J. Soil Sci,1980
3. Moisture and density effect on cone index;Ayers;Trans. ASAE,1982
4. Cone penetration in soil profiling;Baligh;ASCE, J. Geotech. Engr. Div,1980