Reference sources are authoritative works that you refer to to find information on a particular topic, answer questions, and locate facts. They include dictionaries, encyclopaedia, manuals, directories, almanacs, thesauri, and handbooks.
Reference sources can be either in print or electronic.
A collection of Oxford University Press dictionaries, and language and subject reference works including Dictionary of Biology, Dictionary of Zoology, Concise Medical Dictionary
Saunders comprehensive veterinary dictionary by 
Mason's world dictionary of livestock breeds, types and varieties by 
Encyclopedia of Microbiology by 
Topley and Wilson's Microbiology and microbial infections by 
