If you cannot find information on an artist or art work, or need more information, widen your search. Instead of looking directly for the artist, use the catalog to find sources on art of the same time period and country. Your artist might be mentioned in surveys or histories of the period, so check the index in the back of the appropriate books. Even if your artist is not mentioned, you can learn about art in that time and place and analyze the assigned art work based on what you have learned about art of that time.
Biographical dictionaries provide information on an artist's life and work. Art encyclopedias may also be helpful. Dictionaries and encyclopedias are on the reference shelves.
To learn how to write about art (analysis, comparison, etc.) see A Short Guide to Writing About Art by Sylvan Barnet. (ART N 7476 .B37 2007)