Simanungkalit, Lasmaria Nami. “The Based Instructional Materials Development Biology Environmental Issues in Improving Students’ Knowledge on The Basic Concepts Of Ecology”. IJEEM - Indonesian Journal of Environmental Education and Management 2, no. 2 (July 31, 2017): 21–39. Accessed November 6, 2024. https://journal.unj.ac.id/unj/index.php/ijeem/article/view/3715.