Underspecified Query Refinement via Natural Language Question Generation Hassan Sajjad author Patrick Pantel author Michael Gamon author 2012-12 text Proceedings of COLING 2012 Martin Kay editor Christian Boitet editor The COLING 2012 Organizing Committee Mumbai, India conference publication sajjad-etal-2012-underspecified https://aclanthology.org/C12-1143/ 2012-12 2341 2356