Before revision:  Our experiments on the WMT19 metrics tasks for all into-English language directions show that somewhat surprisingly, the addition of diverse paraphrases, even those produced by humans, leads to only small, inconsistent changes in BLEU's correlation with human judgments, suggesting that BLEU's ability to correctly exploit multiple references is limited
After revision:  Our experiments on the into-English language directions show that somewhat surprisingly, the addition of diverse paraphrases, even those produced by humans, leads to only small, inconsistent changes in BLEU's correlation with human judgments, suggesting that BLEU's ability to correctly exploit multiple references is limited