Hasibuan, A. M., and E. surya. “The Effect of an Open-Ended Approach on Students”. International Journal of Sciences: Basic and Applied Research (IJSBAR), vol. 34, no. 1, June 2017, pp. 54-63, https://www.gssrr.org/index.php/JournalOfBasicAndApplied/article/view/7484.