Nikiforos Karamanis Massimo Poesio Chris Mellish Jon Oberlander Evaluating Centering-Based Metrics of Coherence. 391-398 2004 ACL http://acl.ldc.upenn.edu/acl2004/main/pdf/188_pdf_2-col.pdf db/conf/acl/acl2004.html#KaramanisPMO04