052 Subfield $d - Populated place name:

Subfield $d contains the approved form of name for a populated place. In the case of a name established by the U.S. Board on Geographic Names, if a short form of the name has been approved, that form is used in preference to the full form of name.

Example:

651 #0$aMostar (Bosnia and Hercegovina)$vMaps.

052 0#$aBK$dMostar