Purwoto, Asep Dwi, et al. “Development of A Problem-Based Physics E-Module With A Flipped Classroom Approach Using Sigil Software As An Alternative Learning Media During the COVID-19 Pandemic”. Jurnal Penelitian Pendidikan IPA, vol. 8, no. 2, Apr. 2022, pp. 911-7, doi:10.29303/jppipa.v8i2.1198.