RFC and other documents
 RFC 6249 Metalink/HTTP: Mirrors and Hashes
 RFC 5854 The Metalink Download Description Format
 RFC 5988 Link HTTP Header update
 RFC 3864 Link HTTP Header
 RFC 3230 Digest HTTP Header
 RFC 2069 Digest Access Authentication (old)
 RFC 2617 Basic and Digest Access Authentication
 RFC 3986 Uniform Resource Identifier (URI): Generic Syntax
          (obsoletes RFC 2396, 1738, 1808, 2732)

 WARC latest draft (ISO 28500 final costs 122 CHF)
   http://bibnum.bnf.fr/WARC/WARC_ISO_28500_version1_latestdraft.pdf