http://www.rfc-editor.org/rfc/rfc5396.txt
RFC 5396: Textual Representation of Autonomous System (AS) Numbers, G. Huston, G. Michaelson2008-12-01T23:00:00-00:00A textual representation for Autonomous System (AS) numbers is defined as the decimal value of the AS number. This textual representation is to be used by all documents, systems, and user interfaces referring to AS numbers. [STANDARDS-TRACK]