Lubis, N. and Lufri, L. (2022) “Development Of Student’s Activity Sheet (SAS) Based On Problem-Solving About Digestive System Materials In Humans In Class XI SMAN 1 Panyabungan Selatan”, PENBIOS: JURNAL PENDIDIKAN BIOLOGI DAN SAINS, 6(02), pp. 51-58. doi: 10.51673/penbios.v6i02.832.