X00 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 X00 fields only when a topical subject subdivision is added to a name or name/title heading to form an extended subject heading .

Examples:

100 1#$aBrunhoff, Jean de,$d1899-1937$xCharacters$xBabar

100 1#$aTatlin, Vladimir Evgrafovich,$d1885-1953.$tMonument to the Third International$xCopying

100 0#$aNapoleon$bI,$cEmperor of the French,$d1769-1821$xAssassination attempt, 1800 (December 24)

400 1#$aWashington, George,$d1732-1799$xExpedition, 1753-1754