Kogram, C., S. Kowsurat, B. Srimoongkoon, and W. Prasomthong. “Effect of Sowing Date on Yield Component, Biomass Yield and Nutrient Content in Cowpea”. Thai Agricultural Research Journal, vol. 22, no. 1, Mar. 2004, pp. 2-8, doi:10.14456/thaidoa-agres.2004.1.