### MathSciNet

The essential research tool indexing and reviewing the literature of the mathematical sciences with coverage from the 19th century to the present.

### Zentralblatt fur Mathematik / Mathematics Abstracts

An abstracting and indexing service for pure and applied mathematics.

### Google Scholar

A great tool that also does citation indexing.

### Wikipedia

The articles are generally well written and authoritative.

### MacTutor History of Mathematics archive

A source of biographies of mathematicians and the history of mathematics

### Scopus

A citation index covering a wide range of scientific literature with coverage of mathematics

### The Web of Science

A citation index covering a wide range of scientific literature but with limited coverage of mathematics.

### Mathworld

This is a comprehensive and interactive mathematics encyclopedia.

### Jahrbuch-Project Electronic Research Archive for Mathematics

A resource for searching mathematics literature from from 1868 to 1943.

### arXiv

Started in 1991. Now located at Cornell, arXiv.org is a fully automated electronic archive and distribution server for research papers.

### ERIC

This index covers periodicals and other materials in the field of Education, including Education in Mathematics.

### Wolfram Alpha

Based on Mathematica, this search engine allows you to enter a query and returns an answer from structured data.