Komalasary, D., A. Rusilowati, and N. M. D. Putra. “Student’s Creative Zig-Zag Book: Improving Their Concepts Understanding by Using Project Based Learning”. Journal of Primary Education, Vol. 8, no. 2, Sept. 2018, pp. 209-17, https://journal.unnes.ac.id/sju/jpe/article/view/26197.