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Cataloging and Metadata Management

Instructions for Deconstructing MeSH Subjects on NLM MARC 21 Distributed Records

For libraries which wish to structure their own institution's subject headings in the same format as they would appear in the LocatorPlus database, this document provides instructions for deconstructing headings found on NLM MARC 21 records distributed to licensees and resident in OCLC and other utilities following NLM internal cataloging practices.

MeSH headings are identified in the MARC 21 650 field with a second indicator of   "2."   In the following instructions, the MARC 21 650 field is deconstructed according to NLM practice.  All instances of subfields ‡z and ‡v, and certain data in subfield ‡x's in these headings are moved to different 65X fields.

 

1. Any subfield ‡z should be moved to a 651 _2 ‡a. If a subject is repeated with several ‡z's, use a single 650 for the topical heading and multiple 651s.

Example:
Headings in NLM MARC 21 distribution (e.g., on OCLC):
650 12   ‡a Legislation, Medical ‡z United States.
650 22   ‡a Legislation, Medical ‡z Canada.
Deconstructed headings:
650 12   ‡a Legislation, Medical.
651 _2   ‡a United States.
651 _2   ‡a Canada.

2. Any valid MeSH Publication Type (PT) appearing in ‡v should be moved to a 655  _2 ‡a. If a subject is repeated with several ‡v's, use a single 650 field for the subject and multiple 655 fields.

Example:
Headings in NLM MARC 21 distribution (e.g., on OCLC):
650 12   ‡a Heart Diseases ‡v Periodicals.
650 22   ‡a Heart Diseases ‡v Congresses.
Deconstructed headings:
650 12   ‡a Heart Diseases.
655 _2   ‡a Periodicals.
655 _2   ‡a Congresses.
Headings in NLM MARC 21 distribution (e.g., on OCLC):
650 12   ‡a Health Status Indicators ‡v Tables.
650 22   ‡a Mortality ‡v Tables.
650 22   ‡a Epidemiologic Methods.
Deconstructed headings:
650 12   ‡a Health Status Indicators.
650 22   ‡a Mortality.
650 22   ‡a Epidemiologic Methods.
655 _2   ‡a Tables.
Headings in NLM MARC 21 distribution (e.g., on OCLC):
650 12   ‡a Clinical Medicine ‡v Case Report.
650 22   ‡a Clinical Medicine ‡v Examination Questions.
Deconstructed headings:
650 12    ‡a Clinical Medicine.
650 22    ‡a Case Report.
655 _2    ‡a Examination Questions.

3. Most data in the ‡x subfield should remain in the 650 field.

Example:
Headings in NLM MARC 21 distribution (e.g., on OCLC):
650 12  ‡a Hip Joint ‡x surgery.

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