J.H. Jaman, R. Abdulrohman, A. Suharso, N. Sulistiowati, I.P. Dewi "Sentiment Analysis on Utilizing Online Transportation of Indonesian Customers Using Tweets in the Normal Era and the Pandemic Covid-19 Era with Support Vector Machine", Advances in Science, Technology and Engineering Systems Journal, vol. 5, no. 5, pp. 389-394 (2020).