There are also lots of studies for cross-domain sentiment analysis (Blitzer et al., 2007;Tan et al., 2007;Li et al., 2009;Bollegala et al., 2011;He et al., 2011;Glorot et al., 2011).
most of them focused on coarse-grained document-level sentiment classification, which is different from our fine-grained word-level extraction.