7XX Heading Linking Entries - General Information (Variable Data Field)

Definition and scope:

The 7XX Heading Linking Entry fields provide a machine link within a system between equivalent headings whether they are structured in the same or different form, are from the same or different authority files or printed thesauri, or whether they exist as separate authority records. The inclusion of a linking entry field in an established heading or established heading and subdivision record for a name , name/title , uniform title , topical term , form term, or extended subject heading or in an established heading record for an authorized subject subdivision may be used to relate such headings as:

equivalent names in a multilingual thesaurus

Example: National Library of Canada English heading Francis, of Assisi, Saint, 1182-1226 and National Library of Canada French heading François, d'Assise, saint, 1182-1226

equivalent topical term headings in different authority systems

Example: Library of Congress Subject Headings (LCSH) headings Medical referral and Medical consultation and Medical Subject Headings (MeSH) heading Referral and Consultation

a topical term heading (field 150 ) and the same or similar term used as a subject subdivision (field 78X )

Example: established term History and the subject subdivision History

Example: established term Twentieth century and the subject subdivision 20th century

a geographic name heading (field 151 ) and the indirect form of that name used as a geographic subject subdivison (field 751 )

Example: established heading Rome (N.Y.) and the subject subdivision New York (State)--Rome.

a genre/form term heading (field 155 ) and the same or similar term used as a form subject subdivison (field 755 )

The 7XX field tag identifies whether the heading linking entry field contains an established heading (fields 700-755 ) or an authorized subdivision heading (fields 780-785 ). The second indicator or subfield $2 identify the authority system to which the heading in field 7XX belongs. Subfield $0 (Record control number) contains the system control number of the related record when a separate MARC authority record exists for the 7XX heading.

A relationship that cannot be adequately expressed by the 700-785 linking entry fields is described textually in field 788 .

Guidelines for applying content designators:

Guidelines for the second indicator position (Subject heading system/thesaurus), subfield $w (Control subfield), and subfield $2 (Source of heading or term) in the 7XX fields, as well as special instructions for field 788 are provided below. All other content designators in the 7XX fields are defined in the specific fields and in the X00-X85 General Information sections for each type of heading.

For indicator and subfield code definitions and examples, National level (NLR) record requirements , and designator repeatability , see table below. An asterisk ( * ) in the column indicates that the requirement varies. See table in the specific field.:

Input conventions:

The general input conventions for the 7XX fields are provided in the specific fields and in the X00-X85 General Information sections for each type of heading.

Order of subfields

Display constants for 7XX Linking Entries

Content designator history:

Subfields $u - Record control number [obsolete] [USMARC only]

$v - Record control number [obsolete]

$0 - Record control number [new]

$v - Form subdivision [redefined] [USMARC only]

From 1993 to 1995, subfield $v was defined as Record control number in the 7XX Heading Linking Entry fields. In 1995, subfield $v was redefined as Form subdivision and subfield $u was defined as Record control number. In 1997, $0 was defined as Record control number and $u was made obsolete.

9XX - Equivalent Headings [obsolete, 1997] [CAN/MARC only]: The 9XX heading fields were made obsolete in 1997 since the USMARC 7XX fields were already defined for equivalent headings.

LC guidelines for usage:

7XX Heading Linking Entries [General Information]

Related MARC fields or documents:

X00 Personal Names - General Information

X10 Corporate Names - General Information

X11 Meeting Names - General Information

X30 Uniform Titles - General Information

X50 Topical Terms - General Information

X51 Geographic Names - General Information

X55 Genre/Form Terms - General Information

X80 General Subdivisions - General Information

X81 Geographic Subdivisions - General Information

X82 Chronological Subdivisions - General Information

X85 Form Subdivisions - General Information

MARC Code List for Organizations

MARC Code Lists for Relators, Sources, Description Conventions

See also:

7XX Heading Linking Entries

Variable Data Fields