Question: Which datasets are used?
Answer: Reuters,  BBCSport, Polarity, Subjectivity, MPQA, IMDB, TREC, SST-1, SST-2, Yelp2013
Alternative answer:  Reuters, BBCSport BIBREF30, Polarity BIBREF31, Subjectivity BIBREF32, MPQA BIBREF33, IMDB BIBREF34, TREC BIBREF35, SST-1 BIBREF36, SST-2 BIBREF36, Yelp2013 BIBREF26