Generating Indicative-Informative Summaries with SumUM Horacio Saggion author Guy Lapalme author 2002 text journal article Computational Linguistics continuing MIT Press Cambridge, MA periodical academic journal saggion-lapalme-2002-generating 10.1162/089120102762671963 https://aclanthology.org/J02-4005/ 2002 28 4 497 526