Online reference resources include online dictionaries, encyclopedias, atlases, almanacs. These resources are helpful for reseach when you want to find information about topics, locate facts, and answer questions.
The Princeton Encyclopedia of American Political History by 
Twentieth-Century War and Conflict a Concise Encyclopedia by 
One of the most trusted sources of information on any topic used in research to provide background information.
The collection contains about 125 dictionaries, language reference, and subject reference works.
Slected Titles from Oxford Reference Online
Oxford Academic
Books from Oxford Scholarship Online migrated to Oxford Academic.The collection of Oxford Handbooks is one of the most prestigious and successful strands of Oxford’s scholarly publishing, containing in-depth, high-level articles by scholars at the top of their fields. Currently we have unlimited access to 3 of the packages - Literature, Classical Studies, and History.
Archaeology by 
Encyclopedia of the Industrial Revolution in World History by 
Global Voices, Global Visions by
Multiculturalism. Bibliography.
War in the Balkans by