750 Established Heading Linking Entry

Field definition and scope:

Field 750 contains a topical term that is equivalent to the 150 topical term or 180 general subdivision heading field of the same record. It links headings within a system or from different thesauri or authority files.

The National level record requirement for this field is Optional.

Field 750 is repeatable.

Guidelines for applying content designators:

The content designators identify the subelements occurring in topical term and node label headings constructed according to generally accepted thesaurus-building conventions (e.g., Library of Congress Subject Headings).

Topical terms include occupation and function terms that are used as the lead element of subject or added entry access fields in bibliographic records.

A topical term that is authorized for use only as a subject subdivision part of an extended subject heading is contained in a 180 (General Subdivision) or 182 (Chronological Subdivision) field.

For indicator and subfield code definitions and examples, National level (NLR) record requirements, and designator repeatability, see table below:

Position	Description	NLR	Repeatability
Field 750	Established Heading Linking Entry - Topical Term	O	R
Indicator:
First	Undefined; contains a blank	M

Second	Thesaurus	M
0	Library of Congress Subject Headings/Name authority file	A
1	LC subject headings for children's literature	A
2	Medical Subject Headings/NLM name authority file	A
3	National Agricultural Library subject authority file	A
4	Source not specified	A
5	Canadian Subject Headings/LAC name authority file	A
6	Répertoire de vedettes-matière	A
7	Source specified in subfield $2	A

Subfield code:
$a	Topical term or geographic name entry element	M	NR
$b	Topical term following geographic name entry element	A	NR
$g	Miscellaneous information	A	R
$i	Relationship information	A	R
$v	Form subdivision	A	R
$w	Control subfield	A	NR
	/0 Link display	M
	/1 Replacement complexity	A
$x	General subdivision	A	R
$y	Chronological subdivision	A	R
$z	Geographic subdivision	A	R
$0	Authority record control number or standard number	A	R
$1	Real World Object URI		R
$2	Source of heading or term	A	NR
$4	Relationship	O	R
$5	Institution to which field applies	A	R
$6	Linkage	A	NR
$8	Field link and sequence number	O	R

See: Examples for this field.

Input conventions:

Ambiguous headings (what is considered a "topical term")

Display constant for X50 fields

Display constants for 7XX Linking Entries

Content designator history:

Subfield $g - Miscellaneous information [new, 2014]

Subfield $i - Relationship information [new, 2014]

Subfields $u - Record control number [obsolete, 1997] [USMARC only]

$v - Record control number [redefined, 1995] [USMARC only]

$0 - Record control number [new, 1997]

$0 - Record control number [redefined, 2010]

$v - Form subdivision [redefined, 1995] [USMARC only]

$3 - Authority record control number [obsolete, 1997] [CAN/MARC only]

In USMARC, from 1993 to 1995, subfield $v was defined as Record control number in the 7XX Heading Linking Entry fields. When subfield $v was adapted for form subdivisions in MARC bibliographic and authority heading fields in 1995, subfield $v was redefined as Form subdivision and subfield $u was defined as Record control number. In 1997, subfield $0 was added as Record control number in 5XX and 7XX fields and $u was made obsolete.

Subfield $w/1 - Replacement complexity [new, 2002]: In 2002, subfield $w/1 was defined with the following codes: a (Heading replacement does not require review); b (Heading replacement requires review); and n (Not applicable).

Subfield $1 - Real World Object URI [new, 2017]

Subfield $4 - Relationship code [new, 2014]

Subfield $4 - Relationship code [renamed, 2017] [redescribed, 2017]: Subfield $4 was renamed to Relationship and redescribed to allow for the recording of relationship URIs in addition to MARC and non-MARC codes.

LC Guidelines:

750 Established Heading Linking Entry - Topical Term

DCM Z1 Instructions:

7XX Heading Linking Entries