Pintubatu, Rumanti, et al. “Improving the Ability to Write Formal Letters in Elementary School Students Through Contextual Learning (CTL)”. REKOGNISI : Jurnal Pendidikan Dan Kependidikan (E-ISSN 2599-2260), vol. 6, no. 2, Dec. 2021, pp. 11-15, https://jurnal.unusu.ac.id/index.php/rekognisi/article/view/144.