1. L. J. Bobb, Electrostatic Speaker, US Patent 3654403 (1972).
2. Transparent flat panel piezoelectric speaker;Kumada;US Patent,1980
3. Improvements of modal max high-fidelity piezoelectric audio device;Woodard;NASA Tech. Briefs,2005
4. The distributed-mode loudspeaker (DML) as a broad-band acoustic radiator;Harris;Proc. Audio Eng. Soc.,1997
5. H. Azima, N. Harris, and M. Colloms, Loudspeakers Comprising Panel-form Acoustic Radiating Elements, US Patent 6144746 (1996).