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 December 30, 2024. http://iapress.org/index.php/soic/article/view/soic.20180307.