Other curated sets of COVID-19 papers are also available, e.g. the WHO’s COVID-19 database or the Centers for Disease Control and Prevention (CDC)’s COVID-19 research articles database(https://www.cdc.gov/library/researchguides/2019novelcoronavirus/researcharticles.html). These databases overlap with other corpora; for example, the WHO database is ingested by CORD-19 and much of the CDC database overlaps with PubMed and PMC, also sources of papers in CORD-19 and LitCovid. The CDC database also provides a complementary document collection of white papers and technical reports.