MathSciNet provides access to a database of reviews, abstracts and bibliographic information for the mathematical sciences literature from 1940 to the present.
arXiv.org is an electronic archive that provides articles in areas of physics, mathematics, non-linear science and computer science. arXiv is maintained and operated by the Cornell University Library with guidance from the arXiv Scientific Advisory Board.
Zentralblatt MATH is an abstracting and reviewing service in pure and applied mathematics. The MATH Database contains entries drawn from serials and journals.