Note that RFC 6241 obsoletes RFC 4741. Its definition can be found in RFC 1644 (that obsoletes RFC 1379). Standard IEEE 802.1D-2004 incorporates RSTP and obsoletes the original STP standard. This directive obsoletes the X-Frame-Options directive. Cairo obsoletes almost all uses of libart. NYAC Founding Fathers, Princeton Obsoletes, Tri-City Canadians and Tsunami/Olde Quakers.