Powergrading: a Clustering Approach to Amplify Human Effort for Short Answer Grading Sumit Basu author Chuck Jacobs author Lucy Vanderwende author 2013 text journal article Transactions of the Association for Computational Linguistics continuing MIT Press Cambridge, MA periodical academic journal basu-etal-2013-powergrading 10.1162/tacl_a_00236 https://aclanthology.org/Q13-1032/ 2013 1 391 402