1. BLEASDALE, J. K. A. (1973). Plant Physiology in Relation to Horticulture, Macmillan, London, 144 pp
2. JONES, H. A. and EMSWELLER, S. L. (1934). The use of flies as onion pollinators, Proc. Am. Soc. hort. Sci., 31, 160–164
3. KHO, Y. O. and DE BRUYN, J. W. (1962). Gametocidal action of dichioroacetic acid, Euphytica, 11, 287–292
4. KRAM, A. (1954). The use of honey-bees and bumble-bees in breeding work, Euphytica, 3, 97–107
5. THOMPSON, R. C. (1938). Genetic relations of some color factors in lettuce, USDA Tech. Bul., 620