Sanigraha, Beni, and Ikhwan Setiawan. “The Improvement of Students’ Understanding in Spring Energy Concept through Constructivisme Model of Learning”. Wahana Journal of Action Research 1, no. 1 (May 11, 2019): 1-9. Accessed September 19, 2019. http://jurnal.sman1parung.sch.id/index.php/jar/article/view/2.