The second baseline, referred as "NMT + Document Translation", is to treat the weakly aligned doc-   10.9 14.6 ---- NMT (Lample et al., 2018) 17.2 21.0 19.7 20.0 21.2 19.5 PBSMT (Lample et al., 2018) 17.9 22.9 --22.0 23.7 PBSMT + NMT (Lample et al., 2018) 20  uments as two long sentences and use them as a bilingual sentence pair to train NMT models.
2) We leverage the topic consistency of two weakly paired documents and learn the sentence translation model by constraining the word distribution-level alignments.