1. Alexandrous, A. and Earl, R., In situe determination of the precompaction stress of a soil, Journal of Agricultural and Engineering Research, No.61 (1995), pp.67–72.
2. Boon, N. E., Yahya, A., Kheiralla, A. F., Wee, B. S. and Gew, S. K., A Tractor-mounted, Automated Soil Penetrometer–shearometer Unit for Mapping Soil Mechanical Properties, Biosystems Engineering, Vol.90, No.4 (2005), pp.381–396.
3. Cho, Y., Lee, D. H., Park, W. and Lee, K. S., Development of a Real-Time Measurement System for Horizontal Soil Strength, Journal of Biosystems Engineering, Vol.40, No.3 (2015), pp.165–177.
4. Cho, Y., Lee, D., Park, W. and Lee, K., Performance Test of a Real-Time Measurement System for Horizontal Soil Strength in the Field, Journal of Biosystems Engineering, Vol.41, No.4 (2016), pp.304–312.
5. Garciano, L. O., Upadhyaya, S. K., Jahn, B. R. and Jones, R. A., Development of an Instrumented Portable Soil Test Device That Measures Shear, Sinkage, and Friction Parameters of Soil in Situ, American Society of Agricultural and Biological Engineers, Vol.55, No.1 (2012), pp.5–13.