Characterizing English Variation across Social Media Communities with BERT Li Lucy author David Bamman author 2021 text journal article Transactions of the Association for Computational Linguistics continuing MIT Press Cambridge, MA periodical academic journal lucy-bamman-2021-characterizing 10.1162/tacl_a_00383 https://aclanthology.org/2021.tacl-1.33/ 2021 9 538 556