Galindro, Anibal, and Delfim F. M. Torres. “A Simple Mathematical Model for Unemployment: A Case Study in Portugal With Optimal Control”. Statistics, Optimization & Information Computing 6, no. 1 (February 27, 2018): 116-129. Accessed November 15, 2024. http://47.88.85.238/index.php/soic/article/view/soic.20180307.