Fauzi, I., I. Suhendra, L. M. N. Rizkiya, S. Sartono, and A. Safa’at. “Didactic Design on the Circumference and Area of Plane in Grade 4 Elementary Education”. International Conference on Elementary Education, Vol. 2, no. 1, Mar. 2020, pp. 365-76, https://proceedings.upi.edu/index.php/icee/article/view/637.