Bustami, Y., L. Leliavia, N. Elisabeth, A. Gandasari, and D. Ratnasari. “Contextual Teaching learnıng in Human Digestive System: The Contribution of Critical Thinking Skills”. Biosfer: Jurnal Pendidikan Biologi, Vol. 13, no. 1, May 2020, pp. 101 -113, doi:10.21009/biosferjpb.v13n1.101-113.