Trowbridge, S., Ed., Lear, E., Ed., Fishman, G., Ed., and S. Bradner, Ed., "Internet Engineering Task Force and International Telecommunication Union - Telecommunication Standardization Sector Collaboration Guidelines", RFC 6756, DOI 10.17487/RFC6756, September 2012, <https://www.rfc-editor.org/info/rfc6756>.