db/journals/sigir/SilversteinHMM99.html Craig Silverstein Monika Rauch Henzinger Hannes Marais Michael Moricz Analysis of a Very Large Web Search Engine Query Log. 6-12 1999 33 SIGIR Forum 1 db/journals/sigir/sigir33.html#SilversteinHMM99 forum/33-1/P006.pdf