@article{CTT100759007,
  author = {Hidetaka Kamigaito and Taro Watanabe and Hiroya Takamura and Manabu Okumura and Eiichiro Sumita},
  title = {Hierarchical Back-off Modeling of Hiero Grammar based on Non-parametric Bayesian Model},
  journal = {the Journal of Information Processing},
  year = 2017,
}

@article{CTT100741503,
  author = {Hidetaka Kamigaito and Taro Watanabe and Hiroya Takamura and Manabu Okumura},
  title = {Unsupervised Word Alignment Using Frequency Constraint in Posterior Regularized EM},
  journal = {自然言語処理},
  year = 2016,
}