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Control subfield ‡w

Control subfield ‡w in the 4xx and 5xx fields contains 4 bytes (designated as ‡w/0, ‡w/1, etc). It provides information about a specific relationship between a heading (1xx field) and tracing (4xx or 5xx field).

  • Use to indicate whether special instructions apply to the display of the heading in the 4xx or 5xx field.
  • Use to indicate whether a tracing is restricted to the reference structure of a particular type of authority.
  • Each character position has a list of coded values that pertain to it. See the table below.
  • The meaning of a value depends on the character position in which it appears.

The code definitions are position-dependent. Coding any character position with a value other than n (not applicable) mandates coding the preceding positions. Succeeding positions need not be coded. If all 4 positions contain n, subfield ‡w does not appear.

Control subfield ‡w character positions in 4xx and 5xx fields

Ind = Indicator  |  SFC = Subfield code  |  R = Repeatable  |  NR = Nonrepeatable  |  Blank = Blank

byte code description


Special Relationship

  • Specifies the relationship between the heading in a 1xx field and a heading in a 4xx or 5xx field that is more specific than the relationship implicit in the tag
a Earlier heading
b Later heading
d Acronym
f Musical composition
g Broader term
h Narrower term
i Reference instruction phrase in subfield ‡i
n Not applicable
r Relationship designation in subfield ‡i or ‡4


Tracing Use Restriction

  • Specifies the authority reference structure in which the use of a 4xx or 5xx field to generate a cross reference is appropriate
  • When the tracing reference structure use differs from the use of the heading in the 1xx field, a tracing use restriction code in subfield ‡w/1 enables suppression or generation of the cross reference as required for the type of reference structure
a Name reference structure only
b Subject reference structure only
c Series reference structure only
d Name and subject reference structures
e Name and series reference structures
f Subject and series reference structures
g Name, subject, and series reference structures
n Not applicable


Earlier Form of Heading

  • Indicates whether the heading in a 4xx field is an earlier form in which the name or subject was established either in the relevant national authority file or in an authority file other than the national authority file
a Pre-AACR2 form of heading (national name authority file)
e Earlier established form of heading (national authority file)

Not applicable (tracing is not the earlier form of heading)

  • Until all pre-1981 tracings have been evaluated, some 4xx fields carry earlier codes: b (AACR1), c (AACR2), or d (AACR2- compatible)
o Earlier established form of heading (other authority file)


Reference Display

  • Enables the generation or suppression of a cross reference from a 4xx or 5xx field
a Reference not displayed
b Reference not displayed, field 664 used
c Reference not displayed, field 663 used
d Reference not displayed, field 665 used
n Not applicable (reference displayed from tracing

Control subfield ‡w in 7xx fields

Control subfield ‡w in the 7xx fields contains one byte (designated as ‡w/0). It controls the generation of a link display from a 700–785 field. Use subfield ‡w to suppress the display. Subfield ‡w has 4 values.

Control subfield ‡w character position in 7xx fields

Ind = Indicator  |  SFC = Subfield code  |  R = Repeatable  |  NR = Nonrepeatable  |  Blank = Blank

byte code description

Link Display

  • Controls the suppression of a link display from a 700–785 field
  • Use subfield ‡w if the display is to be suppressed
a Link not displayed
b Link not displayed, field 788 used
c Link not displayed, non-7xx field used
n Not applicable


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