Recognizing Contextual Polarity: An Exploration of Features for Phrase-Level Sentiment Analysis Theresa Wilson author Janyce Wiebe author Paul Hoffmann author 2009-09 text journal article Computational Linguistics continuing MIT Press Cambridge, MA periodical academic journal wilson-etal-2009-articles 10.1162/coli.08-012-R1-06-90 https://aclanthology.org/J09-3003/ 2009-09 35 3 399 433