PMC:7795804 / 19467-19675 JSONTXT

{"project":"LitCovid-sentences","denotations":[{"id":"T115","span":{"begin":21,"end":197},"obj":"Sentence"}],"namespaces":[{"prefix":"_base","uri":"http://pubannotation.org/ontology/tao.owl#"}],"text":"rencing challenging. Moreover, the survey sampling was based on an online invitation, which does not allow for generalization because the population that does not use the Internet was not explored.\nIndeed, a "}