Prasetyo, K., Y. Sukestiyarno, and A. N. Cahyono. “The APOS Content Basic Algebra Module to Improve the Learning Autonomy of Achieving Mathematics Connection Skills”. Unnes Journal of Mathematics Education Research, Vol. 10, no. 2, Dec. 2021, pp. 136-43, https://journal.unnes.ac.id/sju/ujmer/article/view/45485.