1. Hoare, A. H. (1945). Vegetable Crops for Market. Crosby Lockwood & Son Ltd. London.
2. Johnstone, K. (1948). Vegetable Culture. Thomas Nelson & Sons Ltd. London.
3. Ministry of Agriculture and Fisheries(1942). Bulletin No. 120, Root Vegetables.
4. Ministry of Agriculture and Fisheries(undated). Dig for Victory, Leaflet No. 6.
5. Snedecor, F. W. (1946). Statistical Methods. Iowa State College Press.