Chemistry has been called the central science because it overlaps a number of other scientific disciplines, bridging physics and the biosciences. Published findings about modern chemistry date from the eighteenth century and have increased tremendously in volume since World War II. In 1946, Chemical Abstracts Service (CAS) included in its flagship publication, Chemical Abstracts, references to 49,578 documents; in 1997, the number was 716,564. Chemists pride themselves on their skill in using the literature of chemistry despite its enormous size and complexity. They have made extraordinary contributions to the organization of chemical information, which has had a major impact on the information retrieval practices in other scientific disciplines.