1. United States Patent, System and method for graphically displaying and navigating through web based interactive voice system, Dec. 2004
2. United States Patent, Method and system for graphicallydisplaying and navigating through an interactive voice response menu, Nov. 15, 1995
3. Wikipedia, the free encyclopedia, Interactive voice response, pp. 1–4,10 Oct. 2008
4. D. J. Allstot and W.C. Black, Jr., “Technology design consideration for MOS switched capacitor filter systems,” Proc. IEEE, vol. 71, no. 8, pp. 967-986, Aug. 1983
5. R. W. Brodersen, P. R. Gray, and D. A. Hodges, “MOS switched capacitor filters,” Proc. IEEE, vol. 67, no.1, pp. 61-75, Jan. 1979