Fatima Zahra Lahdachi, et al. “Nitrogen Fixing Potential of Acacia Gummifera At Different Ages Inoculated With Rhizobium Isolates”. Global Journal of Science Frontier Research, vol. 19, no. D2, Jan. 2019, pp. 1-9, https://journalofscience.org/index.php/GJSFR/article/view/2498.