X11 Subfield $x - General subdivision:

Subfield $x contains a subject subdivision that is not more appropriately contained in subfield $v (Form subdivision), $y (Chronological subdivision), or $z (Geographic subdivision).  Subfield $x is appropriate in the X11 fields only when a topical subject subdivision is added to a name or name/title heading to form an extended subject heading.

Examples:

111  2#  $aNew Mexico State Fair$xFinance

111  2#  $aNew York World's Fair$d(1939-1940)$xBuildings

111  2#  $aOlympic Games$n(11th :$d1936 :$cBerlin, Germany)$xAnniversaries, etc.