• BIND 9 Administration, & Reference Manual.
• NSD DNS Server Tutorial
• Unbound DNS Server Tutorial
• DNS Verify Domain Script, Tool
• Root Servers, and their Locations.

Online documentation:

• Online UNIX man pages Online UNIX man(ual) pages.
• Online application documentation,
  Documentation related to a wide variety of freely available, extremely useful applications.

A growing list of HOW TO's, for DNS / BIND, networks, LAN's, and related.

 See also: DNS How to and DNS tools