5T C Thakun, R J Godwin. Design of extended ring dynamometer for rotary tillage studies [J]. AMA, 1998, 19(3): 16-21.
6M N O'Dogherty. A dynamometer to measure the forces on a sugar beet to Qing knife [M]. J Agri Engng Res, 1975.Determi- nation of the Force of Curved Sub-soiling Shovel Based on Oc- tagonal Ring sensor.