1. Apparatus for coupling agricultural implements to tractors and automatically regulating depth of work,1925
2. Field performance of tractor draught control systems;Cowell;J. agric. Engng Res.,1967
3. Automatic control of tractor mounted implements—an implement transfer function analyser;Cowell;J. agric. Engng Res.,1969
4. Automatic control of tractor mounted implements;Cowell,1970