Munawaroh, Siti, Yohanes Sukestiyarno, and Masrukan Masrukan. “High School Mathematics Curriculum Development Integrated With Character Education Within Project Assessment As Spiral System Leveled”. Unnes Journal of Mathematics Education 6, no. 2 (August 30, 2017): 163-173. Accessed August 6, 2020. https://journal.unnes.ac.id/sju/index.php/ujme/article/view/12969.