Tumasjan, A., T. Sprenger, P. Sandner, and I. Welpe. “Predicting Elections With Twitter: What 140 Characters Reveal about Political Sentiment”. Proceedings of the International AAAI Conference on Web and Social Media, vol. 4, no. 1, May 2010, pp. 178-85, https://ojs.aaai.org/index.php/ICWSM/article/view/14009.