Sidauruk, A., D. E. Silalahi, and Herman. “The Effect of Problem Based Learning (PBL) on Writing Recount Text at Grade Ten of SMK Negeri 2 Pematangsiantar”. Journal of English Teaching As a Foreign Language, vol. 6, no. 1, June 2020, pp. 29-43, https://ejournal.uhn.ac.id/index.php/jetafl/article/view/109.