Yubin Kim 0001 Reyyan Yeniterzi Jamie Callan Overcoming Vocabulary Limitations in Twitter Microblogs. 2012 TREC http://trec.nist.gov/pubs/trec21/papers/CMU_Callan.microblog.final.pdf conf/trec/2012 db/conf/trec/trec2012.html#KimYC12