Guebel, D. V., and N. V. Torres Darias. “Optimization of the Citric Acid Production by Aspergillus Niger through a Metabolic Flux Balance Model”. Electronic Journal of Biotechnology, vol. 4, no. 1, Apr. 2001, pp. 0-0, https://www.ejbiotechnology.info/index.php/ejbiotechnology/article/view/v4n1-2.