Ellena, Raissa Citra, and Dewi Retno Suminar. “Effectiveness Cooperative Learning Numbered Heads Together to Improve the Social Skills of Kindergarten’s Student”. International Journal of Social Sciences and Humanities Invention 5, no. 1 (January 30, 2018): 4344–4349. Accessed March 29, 2024. http://valleyinternational.net/index.php/theijsshi/article/view/1063.