Al-Jbawi, E., W. Sabsabi, G. Gharibo, and A. E.-M. Al-Sayed Omar. “Effect of Sowing Date and Plant Density on Bolting of Four Sugar Beet (Beta Vulgaris L.) Varieties”. International Journal of Environment, vol. 4, no. 2, June 2015, pp. 256-70, doi:10.3126/ije.v4i2.12647.