Reference sources are helpful in locating many types of specific information. They may provide a brief definition of an unfamiliar term, a more in-depth summary of a concept, or a comprehensive treatment of a subject. Some provide statistical information or physical data in the form of tables, graphs, and charts. Many reference sources serve as tools for accessing more information about a topic. The Timken Science Library has many reference sources that will be useful for locating information in each of the science disciplines.