The Encyclopedia of Arabic Language and Linguistics is a major multi-volume reference work. It is a unique collaboration of hundreds of scholars from around the world and covers all relevant aspects of the study of Arabic, dealing with all levels of the language (pre-Classical Arabic, Classical Arabic, Modern Standard Arabic, Arabic vernaculars, mixed varieties of Arabic).
"[T]his is a remarkable work. The vast majority of entries constitute excellent introductions to their subjects and are written by distinguished scholars...all in all, one must be thankful to the editors, the contributors, and the publisher for this useful volume." Gonzalo Rubio, Diachronica Vol. 25, No. 1, pp. 143-149.