Are You Sure That This Happened? Assessing the Factuality Degree of Events in Text Roser Saurí author James Pustejovsky author 2012-06 text journal article Computational Linguistics continuing MIT Press Cambridge, MA periodical academic journal sauri-pustejovsky-2012-sure 10.1162/COLI_a_00096 https://aclanthology.org/J12-2002/ 2012-06 38 2 261 299