748 Established Heading Linking Entry

Field definition and scope:

Field 748 contains a chronological term that is equivalent to the 148 chronological term or 182 chronological 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 748 is repeatable.

Guidelines for applying content designators:

The content designators identify the subelements occurring in chronological term headings constructed according to generally accepted thesaurus-building conventions (e.g., Faceted Application of Subject Terminology (FAST)).

Chronological terms include dates that are used as the lead element of subject or added entry access fields in bibliographic records.

A chronological term that is authorized for use only as a subject subdivision part of an extended subject heading is contained in a 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 748	Established Heading Linking Entry - Chronological 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	Chronological term	M	NR
$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:

Display constant for X48 fields

Display constants for 7XX Linking Entries

Content designator history:

748 - Established Heading Linking Entry - Chronological Term [new, 2002]

Subfield $i - Relationship information [new, 2014]

Subfield $0 - Record control number [redefined, 2010]

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:

748 Established Heading Linking Entry - Chronological Term

DCM Z1 Instructions:

7XX Heading Linking Entries