1. The Principles of Field Drainage;Nicholson,1942
2. The technique of plaster casts for recording mole channel shape;Talman;Field Drainage Experimental Unit, Tech. Bull. 76/6,1976
3. Materials for mole channel casting: Polyurethane foam as an alternative to Plaster of Paris;Thorburn;Ministry of Agriculture Fisheries and Food, Land Drainage Service Research and Development Report No. 1,1980
4. Subsurface Field Drainage Systems in Drainage Principles and Applications;Cavelaars,1980
5. Thorburn, A. A. Personal communication, 1983