Morales, Armando, Efren Marmolejo Vega, Edgardo Locia Espinoza, Alejo López González, and Angie Damián Mojica. “A Teaching-Learning about Optimization Problems: A Close up through the Use of GeoGebra Software”. INTERNATIONAL JOURNAL OF RESEARCH IN EDUCATION METHODOLOGY 10 (February 20, 2019): 3368-3376. Accessed July 19, 2019. https://cirworld.com/index.php/ijrem/article/view/8090.