David Sontag Amir Globerson Tommi Jaakkola Clusters and Coarse Partitions in LP Relaxations. 1537-1544 2008 NIPS http://books.nips.cc/papers/files/nips21/NIPS2008_0989.pdf conf/nips/2008 db/conf/nips/nips2008.html#SontagGJ08