S. F. Persada, A. Oktavianto, B. Miraja, R. Nadlifatin, P. F. Belgiawan, and A. P. Perwira Redi, “Public Perceptions of Online Learning in Developing Countries: A Study Using The ELK Stack for Sentiment Analysis on Twitter”, Int. J. Emerg. Technol. Learn., vol. 15, no. 09, pp. pp. 94–109, May 2020.