1. Sound Absorption Materials;Zwikker,1949
2. Advances in sound absorption polymer;Zhou;Progress in Chemistry,2004
3. Sound absorption characteristics of polymer micro-particles;Zhou;Polymeric Materials Science and Engineering,2004
4. Parameter of metallic hollow spheres — a porous sound absorbing material;Hbelt,2004
5. Krishan K. Ahuja, United States Patent, 5,777,947.