Meanwhile, word representation models based on subword units, such as characters or word segments, have been shown to perform well in many NLP tasks such as POS tagging (dos Santos and Zadrozny, 2014; Ling et al., 2015) , language modeling (Ling et al., 2015; Kim et al., 2016; Vania and Lopez, 2017) , machine translation (Vylomova et al., 2016; Lee et al., 2016; Sennrich et al., 2016) , dependency parsing (Ballesteros et al., 2015) , and sequence labeling<cite> (Rei et al., 2016</cite>; Lample et al., 2016) .