“Knowledge Level Relationship With Community Behavior Concerning Mask Use During The Covid-19 Pandemic In Langkat District, North Sumatera Province”. Diagnosis Jurnal Ilmiah Kesehatan 16, no. 3 (Agustus 31, 2021): 141–146. Diakses Oktober 12, 2026. https://ojs.institutnh.ac.id/index.php/jikd/article/view/474.