Halbart, G., and J. Collignon. “La Gestion De l’entreprise Dans l’esprit De La Recherche Scientifique”. JORBEL - Belgian Journal of Operations Research, Statistics, and Computer Science 3, no. 3-4 (May 1, 1963): 11–24. Accessed April 19, 2024. https://www.orbel.be/jorbel/index.php/jorbel/article/view/459.