This case-sensitive code system https://www.nlm.nih.gov/mesh defines codes, but no codes are represented here
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The Medical Subject Headings (MeSH) thesaurus is a controlled and hierarchically-organized vocabulary produced by the National Library of Medicine. It is used for indexing, cataloging, and searching of biomedical and health-related information. MeSH includes the subject headings appearing in MEDLINE/PubMed, the NLM Catalog, and other NLM databases. MeSH can be downloaded from https://www.nlm.nih.gov/databases/download/mesh.html MeSH can be browsed here: https://meshb.nlm.nih.gov/search