To test the robustness of the taggers against the OOV problem, we also conduct experiments using artificially constructed unnormalized text by corrupting words in the normal dev set. Again, the CNN tagger outperforms the two baselines by a very large margin. 
 Question: How do they confirm their model working well on out-of-vocabulary problems?
conduct experiments using artificially constructed unnormalized text by corrupting words in the normal dev set