A. Tijjani, S. Muhammad,. “Effect of Plant Growth Regulators on Root Nodulation of Cowpea (Vigna Unguiculata L. Walp)”. Journal of Phytology 1, no. 6 (October 6, 2009). Accessed September 21, 2025. https://updatepublishing.com/journal/index.php/jp/article/view/2045.