„User-Agent”. Netnews Article Format. IETF. новембар 2009. sec. 3.2.13. doi:10.17487/RFC5536. RFC 5536. „Some of this information has previously been sent in non-standardized header fields such as X-Newsreader, X-Mailer, X-Posting-Agent, X-Http-User-Agent, and others”CS1 одржавање: Формат датума (веза)
C. Hutzler; D. Crocker; P. Resnick; E. Allman; T. Finch (novembar 2007). „Email Submission Operations: Access and Accountability Requirements”. Best Current Practice. IETF. Приступљено 24. 8. 2011. „This document does not provide recommendations on specific security implementations. It simply provides a warning that transmitting user credentials in clear text over insecure networks SHOULD be avoided in all scenarios as this could allow attackers to listen for this traffic and steal account data. In these cases, it is strongly suggested that an appropriate security technology MUST be used.”
„User-Agent”. Netnews Article Format. IETF. новембар 2009. sec. 3.2.13. doi:10.17487/RFC5536. RFC 5536. „Some of this information has previously been sent in non-standardized header fields such as X-Newsreader, X-Mailer, X-Posting-Agent, X-Http-User-Agent, and others”CS1 одржавање: Формат датума (веза)