Theresa Wilson Janyce Wiebe Paul Hoffmann Recognizing Contextual Polarity: An Exploration of Features for Phrase-Level Sentiment Analysis. 399-433 2009 35 Computational Linguistics 3 http://dx.doi.org/10.1162/coli.08-012-R1-06-90 db/journals/coling/coling35.html#WilsonWH09