1. ASAE Standard: ASAE S313.1, Soil cone penetrometer;Am. Soc. Agric. Eng.,1983
2. ASTM Standard D5778-95, Standard test method for performing electric friction cone and piezocone penetration testing of soils,1995
3. New hand-held recording pene-penetrometer for soil studies;Anderson;J. Soil Sci.,1989
4. Moisture and density effect on cone index;Ayers;Trans. ASAE,1982
5. Pedotransfer functions and threshold values: from soil characteristics to land qualities;Bouma,1987