At present, learning from one single treebank seems inadequate for further boosting parsing accuracy.
1  studies have recently resorted to other resources for the enhancement of parsing models, such as large-scale unlabeled data (Koo et al., 2008;Chen et al., 2009;Bansal and Klein, 2011;Zhou et al., 2011), and bilingual texts or cross-lingual treebanks (Burkett and Klein, 2008;Burkett et al., 2010;Chen et al., 2010).