pe.usps.com http://pe.usps.com/text/dmm300/508.htm http://pe.usps.com/text/dmm300/508.htm#1132460 http://pe.usps.com/text/dmm300/508.htm#1051804 http://pe.usps.com/text/dmm300/508.htm#1051804 http://pe.usps.com/text/dmm300/508.htm http://pe.usps.com/text/dmm300/508.htm say DMM Chapter 508, Section 1.5.1 USPS website http://pe.usps.com/text/dmm300/508.htm#1052479 http://pe.usps.com/text/dmm300/508.htm#1051804 say