Abidin, Minhajjul, and Heri Retnawati. “A Diagnosis of Difficulties in Answering Questions of Circle Material on Junior High School Students”. Jurnal Penelitian Dan Evaluasi Pendidikan, vol. 23, no. 2, Dec. 2019, pp. 144-55, doi:10.21831/pep.v23i2.16454.