8Gill W Randy, Vanden Berg G E. Soil dynamics in tillage and traction[M]. Agrieuhure Handbook United States Department of Agriculture, 1967:316-320.
9Trousse A C, Humbert R P. Deep tillage in Hawaii: 1. Subsoiling[J]. Soil Sclenoe, 1959,88(3): 15.
10Spoor G, Godwin R J. An experimental investigation into the deep loosening of soil by rigid tiara [J]. Jonmal of Agrieultml Engineering Research, 1978,23(3) : 243-258.
