In "Language Models are Unsupervised Multitask Learners"[0]. Not sure whether it’s "the" GPT-2 paper.
3.7 Translation
> Performance on this task was surprising to us, since we deliberately removed non-English
webpages from WebText as a filtering step. In order to con-
firm this, we ran a byte-level language detector2 on WebText
which detected only 10MB of data in the French language […]
