1. Results of tillage trials carried out in 1981–1987 in Central Italy;Archetti,1988
2. Dinamika fiziko-mekhanicheskie svoistv pochv v sviazi voprosami ikh obrabotki;Bakhtin;Tr. Pochv. Inst. im. V.V. Dokuchaeva,1954
3. The influence of soil strength on the penetration of a loam by plant roots;Barley;Aust. J. Soil. Res.,1968
4. Compaction of Agricultural Soils,1971
5. Use of a low-friction penetrometer to estimate soil resistance to penetration;Bengough,1988