(en) Mick Ekers, Zappa Gear: The Unique Guitars, Amplifiers, Effects Units, Keyboards and Studio Equipment, Bloomsbury Publishing USA, (ISBN978-1-4930-8402-9, lire en ligne), p.304
(en) Joshua D. Reiss et Andrew P. McPherson, Audio Effects: Theory, Implementation and Application, CRC Press, (ISBN978-1-040-06158-9, lire en ligne), p.39
(en) William L. Martens et Marui, Atsushi, «Categories of Perception for Vibrato, Flange, and Stereo Chorus:Mapping out the Musically Useful Ranges of Modulation Rate and Depth for Delay-based Effects», Proc. of the 9thInt. Conference on Digital Audio Effects (DAFx’06), Montreal, Canada, September 18-20, 2006, (lire en ligne).