(2017); Logeswaran and Lee (2018)); and (iii) contextualized word representation (e.g., Cove (McCann et al., 2017), ELMo (Peters et al., 2018).
eLMo (Peters et al., 2018) learns high-quality, deep contextualized word representation using bidirectional language model, which can be directly plugged into standard NLU models for performance boosting.