ISO/IEC 15055:1997 - Information technology -- Telecommunications and information exchange between systems -- Private Integrated Services Network -- Specification, functional model and information flows -- Transit counter additional network feature - 1st edition [ZIP File]. - http://www.iso.org/iso/en/CatalogueDetailPage.CatalogueDetail?CSNUMBER=26335&ICS1=33&ICS2=40&ICS3=35