MARC21       651     Subject Added Entry--Geographic Name (R)
  Subfields: 
             $a   Geographic name
             $v   Form subdivision [NEW]
             $x   General subdivision (R)
             $y   Chronological subdivision (R)
             $z   Geographic subdivision (R)
             $2   Source of heading or term
             $6   Linkage

 Indic/etc.: 1st: Undefined; contains a blank (#)
             2nd: Subject heading system/thesaurus
             0 Library of Congress Subject Headings/LC authority files
             1 LC subject headings for children's literature
             2 Medical Subject Headings/NLM authority files
             3 National Agricultural Library subject authority file
             4 Source not specified
             5 Canadian Subject Headings/NLC authority file
             6 Repertoire des vedettes-matiere/NLC authority file
             7 Source specified in subfield $2