Rip, It's referenced on page 46 in "Total Quality Control" by Feigenbaum (3rd Edition 1983). Rich DeRoeck Supplier Quality Engineer IQA &Calibration Manager Skyworks Solutions Inc. 20 Sylvan Rd Woburn, MA 01801 t:781-376-3058 f:781-376-5234 e:richard.deroeck@skyworksinc.com