[1] Naik D.C., INTERNET standardy a protokoly. První vydání. Computer Press, Praha, 1999, ISBN 80-7226-146-0
[2] Myers J. [Carnegie Mellon], Rose M. [Dover Beach Consulting,
Inc.] ,
RFC 1939 Post
Office Protocol - Version 3, ftp://ftp.isi.edu/in-notes/rfc1939.txt
[3] RFC 1321 - kódovací algoritmus MD5
[4] Crocker D. H. ,
RFC
822 Standard for the Format of ARPA Internet Text Messages,
ftp://ftp.isi.edu/in-notes/rfc822.txt