Sri Murtini, et al. “Increasing Creative Thinking Ability Using Probem Based Learning (PBL) Model”. ICHELSS: International Conference on Humanities, Education, Law, and Social Sciences, vol. 1, no. 1, July 2021, pp. 471-7, https://journal.unj.ac.id/unj/index.php/hispisi/article/view/22194.