> To connect the languages of different groups, we identified a small number of bridge languages, which are usually one to three major languages of each group. In the example above, Hindi, Bengali, and Tamil would be bridge languages for Indo-Aryan languages. We then mined parallel training data for all possible combinations of these bridge languages.
Pretty cool.
https://scontent-arn2-2.xx.fbcdn.net/v/t39.8562-6/122141102_... seems like they actually do improve on a quite a lot of single-pair WMT scores.