PMC:7696151 / 5822-5972 JSONTXT

{"project":"LitCovid-sentences","denotations":[{"id":"T49","span":{"begin":2,"end":57},"obj":"Sentence"},{"id":"T50","span":{"begin":58,"end":137},"obj":"Sentence"}],"namespaces":[{"prefix":"_base","uri":"http://pubannotation.org/ontology/tao.owl#"}],"text":". In total, 133 papers were selected for data extraction. A flowchart illustrating the steps of the study selection is shown in Figure 2.\nIn our revie"}