1. Wirt, L. S. Analysis. Testing, and Design of Lined Ducts Journal of theAcoustical Society of AmericaVol.51,Number 5(Part 1),1972.
2. Jones,M. andParrott,T. Enhanced Broadband Absorption for Duct Liners by Means of Spatially Varying Impedances Proceedings of Noise-Con 93,Williamsburg,VA,May 2-5,1993.
3. Marc, F., Denis, T., and Marie-Annick, G. Actively Enhanced Porous Layers for Free Field Acoustic Absorption Presented at the Third International Conference on Intelligent Materials (Third European Conference on Smart Structures andMaterials),Lyon,France June 3-5,1996.