Kelly Williams (May 11, 2003). "Background of the Guitar-Zither". The Guitar-Zither Clearinghouse. terminology on the "guitar-zither" (patented by Menzenhauer), "chord zither" (referred guitar-zither, appeared in The Oxford Companion to Musical Instruments and The New Grove Dictionary of Musical Instruments), and "chorded zither" (referred Autoharp without trademark infringement with Oscar Schmidt International).
minermusic.com
Gregg Miner & Kelly Williams (July 2011). "Selecting the Term". Fretless Zithers. terminology and taxonomy of the "Fretless Zither" family instruments.
patents.google.com
Guitar-Zither, Specification forming part of Letters Patent No. 520,651, dated May 29, 1894. Application filed April 20, 1893, Serial No.471,147. (No model.), United States Patent Office
