Artists' Biographies: Getting Started

Try looking the artist as both a keyword search and as an author in the Library Search,  
To verify the spelling of an artist's name, as well as to find more information in journal articles, consider using the browse function of Art Full Text
The Union List of Artist Names, or ULAN, is another excellent way to verify the spelling of an artist's name.

Try Oxford Art Online. You will find wonderful articles written by experts on the subject, plus bibliographies of books and articles you can use as a starting point for your research.

* More resources can be found in the Sherman Reference Room