This 1930 pages giant resource on Russian History is very valuable, IMHO. You can see the details on Gale Group's site which published this 4 volume encyclopedia.
Here is a quote from their site:
"Focusing on Russia's history from the time of the Tsars to the present (though a few articles go back earlier), this encyclopedia features 1,500 articles on people, politics, customs, languages, economies, wars, religions, art and literature, science, and geography of Russia and the former Soviet republics. "
--Reference & Research Book News (February 2004)