Hidayati, Siti, et al. “Validity and Practicality of Problem Based Learning (PBL) Model Learning Tools to Improve Students’ Conceptual Understanding”. Prisma Sains : Jurnal Pengkajian Ilmu Dan Pembelajaran Matematika Dan IPA IKIP Mataram, vol. 9, no. 1, June 2021, pp. 82-87, doi:10.33394/j-ps.v9i1.3966.