PMC:7441788 / 21204-21397 JSONTXT

{"project":"LitCovid-sample-sentences","denotations":[{"id":"T160","span":{"begin":0,"end":193},"obj":"Sentence"}],"namespaces":[{"prefix":"_base","uri":"http://pubannotation.org/ontology/tao.owl#"}],"text":"Retrospective nature of the study; The subjects included only men and most of them were black; Despite adjustments to many possible confounding factors, there may still be undiscovered factors."}

{"project":"LitCovid-sentences","denotations":[{"id":"T160","span":{"begin":0,"end":193},"obj":"Sentence"}],"namespaces":[{"prefix":"_base","uri":"http://pubannotation.org/ontology/tao.owl#"}],"text":"Retrospective nature of the study; The subjects included only men and most of them were black; Despite adjustments to many possible confounding factors, there may still be undiscovered factors."}