Noor Afifah Wan Ahmad, W., S. Firdaus Sufahani, M. Abd Hakim Mohamad, M. SaifullahRusiman, M. Zulariffin Md Maarof, and M. Ali lmran Kamarudin. “NON-CLASSICAL OPTIMAL CONTROL PROBLEM: A CASE STUDY FOR CONTINUOUS APPROXIMATION OF FOUR-STEPWISE FUNCTION”. Advances in Differential Equations and Control Processes, Vol. 30, no. 4, Sept. 2023, https://ojs.acad-pub.com/index.php/ADECP/article/view/2417.