The Blackwell Companion to Philosophy.Oxford: Blackwell, 1991-present.
This reference series, centred on analytic philosophy, but also covering important aspects of the continental traditions and of non-Western philosophies, is made up of over fifty volumes each dealing with a particular subject area (e.g. aesthetics, environmental philosophy, philosophy in the Middle Ages) or with a particular philosopher (e.g. Aristotle, Hume). Some volumes are arranged in a dictionary format with entries about people, terms and movements; other volumes are arranged as a collection of essays.