Handayani, T., I. Marzuki, and N. K. . Umam. “The Development of Textbooks On Circumference And Area Of Flat Shapes Material For Grade IV Elementary School”. IJPSE Indonesian Journal of Primary Science Education, vol. 3, no. 1, Nov. 2022, pp. 127-36, doi:10.33752/ijpse.v3i1.3206.