Rindah, Maharani Aji Kharisma, et al. “Excretory System Learning in Senior High School: Comparative Analysis of students’ Problem Solving Skills”. Biosfer: Jurnal Pendidikan Biologi, vol. 12, no. 2, Nov. 2019, pp. 249-57, doi:10.21009/biosferjpb.v12n2.249-257.