Sunaringtyas, Afianita, Mohammad Asikin, and Iwan Junaedi. “The Student’s Analysis of Creative Thinking Process in Solving Open Problems Viewed from Wallas Model on Problem Based Learning Model”. Unnes Journal of Mathematics Education 6, no. 3 (November 30, 2017): 287-293. Accessed October 21, 2020. https://journal.unnes.ac.id/sju/index.php/ujme/article/view/16084.