Cittern - Article describing the instrument and its history; includes modern usage of the name to describe instruments of the mandolin family. [Wikipedia]

Cittern Music in the Sixteenth Century - A brief description, information about tunings, and listings of composers and their works.

English Guittars - An illustrated description of instruments restored by a British luthier.

Renovata Cythara - Dedicated to the Renaissance cittern and related instruments; includes articles, information on music, composers, and history of the instrument, and on modern players and builders.