Encyclopedias provide introductory information to help broaden or narrow the scope of your topic while also supplying keywords and citations needed for further research.
Encyclopedia of Russian History: From the Christianization of Kiev to the Break-up of the U.S.S.R. by 
Encyclopedia of Contemporary Russian Culture by 
The Cambridge Encyclopedia of Russia and the Former Soviet Union by 
The Cambridge history of Russia: The Twentieth Century (Vol. 3) by 
