1. Abrams, B. F., Minor, R. B., McGregor, G. L. and Dolan, J. W., “Expanded PTFE Fiber and Fabric and Method of Making Same,” US Patent 5591526 (1994).
2. Bacino, J., “Porous PTFE Film and a Manufacturing Method Therefor,” US Patent 5476589 (1995).
3. Baumgartner, H. and Loeffler, F., “The Collection Performance of Electret Filters in the Particle Size Range 10 nm-10 μm,”J. Aerosol Sci.,17, 438 (1986).
4. Caldwell, J. M, “Controlling the Porosity and Permeability of a Web,” US Patent 6071602 (1998).
5. Kanaoka, C., Emi, H., Otani, Y. and Iiyama, T., “Effect of Charging State of Particles on Electret Filtration,”Aerosol Sci. Technol.,7, 1 (1987).