Reference sources published by Oxford University Press. Dictionaries, subject reference works, language reference sources and key titles in the Oxford Companion series. Some examples are: the Oxford-Duden German dictionaries, A Dictionary of Psychology, A Dictionary of Zoology, The Oxford Dictionary of Idioms, A Dictionary of Writers and Their Works, Oxford Companion to Western Art, Oxford Companion to U.S.History, Oxford Companion to Music, Oxford Companion to Philosophy, and The Encyclopedia of Popular Music, etc.