An online database of journals and books hosted at the Harvard–Smithsonian Center for Astrophysics in Cambridge, Massachusetts, and funded by NASA. Publications in the ADS cover the fields of astronomy, astrophysics, physics, and geophysics. The ADS provides open access not only to published papers but also to preprints of forthcoming papers. The ADS first went online in 1994.

http://adsabs.harvard.edu/index.html Official ADS website, allowing search of their digital library.