Besides, CRFs can only employ word-level features, which are either hand-crafted or extracted with deep neural networks, such as window-based neural networks (Collobert et al., 2011) and bidirectional Long Short-Term Memory networks (BI-LSTMs) .
we also denoise our gazetteers by removing overlapped entities and using BBN Pronoun Coreference and Entity Type Corpus (weischedel and Brunstein, 2005) as filters 10 .