Peter F. Brown Stephen Della Pietra Vincent J. Della Pietra Robert L. Mercer A Statistical Approach to Sense Disambiguation in Machine Translation. 1991 conf/naacl/1991 HLT http://acl.ldc.upenn.edu/H/H91/H91-1025.pdf db/conf/naacl/naacl1991.html#BrownPPM91