GeoRef contains a vast amount of indexed information, including 3.8 million bibliographic records from more than 3,500 journals covering a wide spectrum of geoscience literature. Other records featured within the database include indexed books, maps, government reports, conference papers, theses, and dissertations. GeoRef is also constantly adding new material to its collection, with more than 100,000 records added annually. Subjects covered include mineralogy, hydrogeology, economic geology, hydrology, environmental geology, marine geology, engineering geology, mineralogy, geochemistry, oceanography, geophysics, and paleontology. Coverage within the database includes the geology of North America from 1666 to the present, as well as global coverage dating back to 1933.