Description of Hand Washing and Mask Wearing Knowledge during the Pandemic in Grade 4-5 School Children at Dolok Nagodang State Elementary School in 2021. jisk [Internet]. 2022 Aug. 31 [cited 2024 Nov. 21];3(2):18-22. Available from: https://ejournal.sumateraconnect.or.id/index.php/jisk/article/view/37