An online version of the Mennonite encyclopedia (ed. Bender et al., 5 vols., REF BX8106 .M37), itself a translation of and expansion on the Mennonitisches Lexikon (ed. Hege und Neff, 4 vols., BX8106 .M4 1913), which is being supplied with a fifth, supplementary volume online.
Historical Dictionary of Lutheranism. Ed. Gassmann.