Nasution, Y. S., and E. Surya. “Application of TPS Type Cooperative Learning in Improving Students”. International Journal of Sciences: Basic and Applied Research (IJSBAR), vol. 34, no. 1, June 2017, pp. 116-25, https://www.gssrr.org/index.php/JournalOfBasicAndApplied/article/view/7564.