ZHANG, E.; ZHANG, W.; JIN, C. RETRACTED: SPOC-based Flipped Classroom of College English: Construction of an Effective Learning Model. International Journal of Emerging Technologies in Learning (iJET), [S. l.], v. 13, n. 01, p. pp. 37–45, 2018. DOI: 10.3991/ijet.v13i01.7513. Disponível em: https://online-journals.org/index.php/i-jet/article/view/7513. Acesso em: 23 jan. 2022.