Maya Ningrum, Desy Tya, et al. “The Effect of Cooperative Learning and Self Confidence on Service Volleyball At SMPN 4 Negara”. JIPES - JOURNAL OF INDONESIAN PHYSICAL EDUCATION AND SPORT, vol. 5, no. 1, July 2019, pp. 63-68, https://journal.unj.ac.id/unj/index.php/jipes/article/view/14657.