How to find dates of creation of famous art works?

Question:

How to find dates of creation of famous art works?

I find myself surfing the web constantly looking for the dates of creation of certain artworks. does anyone know of a good resource or good method to find out the dates of famous paintings? For instance, today I am looking for when was "Mercado de Flores" by Diego Rivera was painted:
http://www.overstockart.com/medefl.html...

Best Answer - Chosen by Asker:

I actually get Diego Rivera books in the art history section of the library.

As a fine arts major, doing my research at the local museums paid off big time.