Written by established scholars, each of the thirteen chapters is an survey of a central theme in Anabaptist/Spiritualist history. The authors describe the current state of scholarship on this theme, suggest future research and include extensive bibliographies. An excellent starting point for in-depth study. An EBSCO eBook.
Five volumes of the classic Mennonite Encyclopedia with some updated articles and bibliography. Watch for indications of which articles have been revised.
Another complete set is available in the General Books North circulating collection. All of the articles in the original four volumes (1955-59) and the fifth volume (1990) are available in the online version, Global Anabaptist Mennonite Encyclopedia Online (GAMEO)New articles and revisions are added.
A Companion to Anabaptism and Spiritualism, 1521-1700 by 
The Mennonite Encyclopedia by 
The Oxford Encyclopedia of the Reformation by 