1. Farm Machinery and Equipment;Smith,1964
2. Physical reactions of soil on plough discs;Gordon;Agricultural Engineering,1941
3. The geometry of discs and soil relationships;McCreery;Agricultural Engineering,1956
4. The geometry of discs and soil relationships;McCreery;Agricultural Engineering,1956
5. Field measurements of forces and moments on wheatland plough discs;Taylor;Transactions of the ASAE,1967