“Knowledge Level Relationship With Community Behavior Concerning Mask Use During The Covid-19 Pandemic In Langkat District, North Sumatera Province”, DJIK, vol. 16, no. 3, hlm. 141–146, Agu 2021, Diakses: Okt 12, 2026. Tersedia pada: https://ojs.institutnh.ac.id/index.php/jikd/article/view/474