"Petroleum" 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.
Naturally occurring complex liquid hydrocarbons which, after distillation, yield combustible fuels, petrochemicals, and lubricants.
This graph shows the total number of publications written about "Petroleum" by people in this website by year, and whether "Petroleum" was a major or minor topic of these publications.
To see the data from this visualization as text, click here.