The SAO/NASA Astrophysics Data System is a digital library portal for researchers in astronomy and physics, operated by the Smithsonian Astrophysical Observatory (SAO) under a NASA grant. The ADS maintains three bibliographic databases containing more than 8.7 million records: Astronomy and Astrophysics; Physics; and arXiv e-prints. It covers journal articles, conference papers, technical reports, books and chapters.
