Reference resources include online dictionaries, encyclopedias, atlases, almanacs. These resources are helpful for research when you want to find information about topics, locate facts, and answer questions.
The Routledge Handbook of Balkan and Southeast European History by 
One of the most trusted sources of information on any topic used in research to provide background information.
The collection contains dictionaries, language reference, and subject reference works.
A Companion to World History by 
Encyclopedia of Eastern Europe by 
Historical Dictionary of Bulgaria by 
Palgrave Dictionary of Emerging Markets and Transition Economics by