Punctuation in X50 fields:

The punctuation of the subelements of a heading is generally dictated by subject heading system/thesaurus rules. These input conventions clarify MARC punctuation practices.

An X50 field does not end with a mark of punctuation unless the field ends with an abbreviation, an initialism, or data that ends with a mark of punctuation.

Examples:

150 ##$aMagazine illustration

150 ##$aSeasonal variations (Economics)

150 ##$aEducation$zWashington (D.C.)

150 ##$aMuseums$zRussia (Federation)

150 ##$aArt, Chinese$yTo 221 B.C.

150 ##$aResearch libraries$zMexico$xSocieties, etc.