"Coal" is a descriptor in the National Library of Medicine's controlled vocabulary thesaurus, MeSH (Medical Subject Headings). Descriptors are arranged in a hierarchical structure, which enables searching at various levels of specificity.
MeSH information
A natural fuel formed by partial decomposition of vegetable matter under certain environmental conditions.

This graph shows the total number of publications written about "Coal" by people in this website by year, and whether "Coal" was a major or minor topic of these publications.
Bar chart showing 468 publications over 25 distinct years, with a maximum of 63 publications in 2018
To see the data from this visualization as text, click here.