1. Godwin RJ. An investigation into the mechanics of narrow tines in frictional soils. PhD thesis, University of Reading, 1974.
2. Modelling soil disturbance due to tillage and traffic;Smith,1989
3. The calculation of passive pressure in two-dimensional soil failure;Hettiaratchi;J Agric Engng Res,1966
4. The calculation of passive soil resistance;Hettiaratchi;Geotechnique,1974
5. Hettiaratchi DRP. The calculation of passive earth pressure. PhD thesis, University of Newcastle-upon-Tyne, 1969.