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Hypertext links in HTML (draft)

      BEGIN or FIRST
         The BEGIN relationship identifies the author- defined start of
         a sequence of documents of which the current document is a
         node. TOP is a functional equivalent to BEGIN when only one of
         these values is specified.

         When REL=BEGIN, the target document is the beginning of the
         sequence.  When REV=BEGIN, the current document is the
         beginning of the sequence.

         If the hypertext link is specified with REL in a LINK element,
         an HTML user agent may present an icon in a tool bar.

[引用: 4.4e. Sequence Links -- Hypertext links in HTML (draft) より]