Mohi-Aldin, Mohammed O., and Aiden M. Hussain. “Optimization of Citric Acid Production from Locally Isolate Fungus Aspergillus Niger by Solid State Fermentation”. Ibn AL-Haitham Journal For Pure and Applied Sciences, vol. 28, no. 2, Mar. 2017, pp. 208-24, https://jih.uobaghdad.edu.iq/index.php/j/article/view/226.