Tracings and References-General Information
MARC 21 Classification
October 2003
"Full" documentation refers to the MARC 21 Format for Classification Data that contains detailed descriptions of every data element, along with examples, input conventions and history sections.
"Concise" documentation refers to the MARC 21 Concise Format for Classification Data that contains abridged descriptions of every data element, along with examples.
Reference fields
Tracing fields
DEFINITION AND SCOPE
A cross reference is used to refer between classification numbers that are constructed
according to the classification scheme that is identified in field 084 (Classification
Scheme and Edition). It leads from an invalid classification number to a valid
classification number or from one valid classification number to another valid
classification number. Tracings or reference note fields are used to direct the user to
another classification number, often for specific aspects of a topic. Cross reference
displays may be generated by combining the contents of a tracing or a reference note
field and field 153 (Classification Number) of a record. In some cases the inputting
library may provide both a tracing and a reference note field and choose to suppress the
tracing for display purposes.
■ TRACING FIELDS
Tracing fields lead directly from one number to another number. A 453 Invalid Number
Tracing field leads from an invalid number to a valid number. A 553 Valid Number Tracing
field leads from one valid classification number to another, often for classification of
certain topics. Cross reference displays generated from the tracing fields are called
simple cross references. In a simple cross reference display, the content of
the 453 or 553 field is the number referred from, and, following a reference
instruction phrase, the content of the 153 field is the number referred to. In
the tracing fields, the reference instruction phrase is associated with a code in
subfield $w/0 (Special relationship) and/or subfield $w/1
(Hierarchical relationship). In unusual cases the reference instruction phrase may be
carried explicitly in subfield $i (Reference instruction phrase).
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| 084 |
0#$alcc [Library of Congress Classification] |
| 153 |
##$aHD1330$cHD1331$hIndustries. Land use. Labor$hLand tenure$jLandlord and peasant |
| 453 |
00$wj$aHD1501.2$hIndustries. Land use. Labor$hAgricultural economics$jLandlord
[An invalid classification number in field 453 leads the user to the valid
classification number span in field 153.] |
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Cross reference display example:
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| Industries. Land use. Labor |
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Agricultural economics |
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Landlord see HD 1330-HD1331
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| [Note: the invalid number in 453$a may be suppressed for
display] |
■ REFERENCE NOTE FIELDS
Reference note fields lead from one classification number to one or more other
classification numbers. A reference note field is used when more complex reference
instruction is needed than can be conveyed by one or more simple cross references
generated from 453 and/or 553 tracing fields. There are two types of reference note
fields: 1) see references (field 253), which refer to a classification number in another
record and 2) see also references, which guide the user to related topics in other valid
classification numbers (field 353).
Cross reference displays constructed from the reference note fields are complex
cross references. In a complex cross reference display, the content of the 153
field of a record is the number referred from, and, following a reference
instruction phrase, the reference note field contains the number(s) referred
to. In the reference note fields, the reference instruction is given as explicit
text in subfield $i (Explanatory text).
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| 008/06 |
b |
| 084 |
0#$addc$c22 [Dewey Decimal Classification] |
| 153 |
##$a621.47$hTechnology (Applied sciences)$hEngineering and allied operations$hApplied physics$hHeat engineering and prime movers$jSolar-energy engineering |
| 253 |
2#$iClass engineering of secondary sources of solar energy with
the secondary source, e.g., generation of electricity from solar radiation$a621.31244$iwind energy$a621.45
[Reference instruction phrase is explicit in 253 subfield $i] |
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Cross reference display example at 621.47:
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| 621.47 Solar-energy
engineering
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Class engineering of secondary sources of solar energy with the secondary source,
e.g., generation of electricity from solar radiation 621.31244, wind energy
621.45 |
GUIDELINES FOR APPLYING CONTENT DESIGNATORS
Guidelines for applying subfield $i (Reference instruction phrase), subfield
$t (Topic) and subfield $w (Control subfield) in the 453 and 553
fields and examples of simple cross reference displays are provided in this section.
Guidelines for applying the content designators for the classification number and
caption portions of the 453 and 553 tracing fields are provided in the X53
Classification Numbers - General Information section.
Guidelines for applying the content designators and examples of complex cross reference
displays for fields 253 and 353 are provided in the individual field descriptions.
■ TRACING FIELDS-SIMPLE CROSS REFERENCES
Simple cross references are generated for display from tracing fields. Displays may vary
from one system to the next; those shown below are only suggestions. The content of
subfield $i and subfield $w determine the reference instruction
phrase used with the tracing. The character positions defined for subfield $w
are described here. Subfield $t (Topic) provides additional information about
the use of the classification number.
$i - Reference instruction phrase Special reference instruction phrase that may be used in a cross reference display
when the generation of a reference instruction phrase based on a code in control
subfield $w/0 is not possible. When a tracing field contains subfield
$i, subfield $w/0 contains code i (Reference instruction
phrase in subfield $i).
$t - Topic Topics for which the tracing is appropriate. If the topic is the same as the
caption in field 153 (Classification Number), subfield $j (Caption),
the topic need not be repeated in subfield $t. However, if the topic is
the same as the caption of the number referred to in subfield $j of
field 453 or 553, the topic is still contained in subfield $t to
facilitate a display of the tracing.
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| 084 |
0#$alcc [Library of Congress Classification]
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| 153 |
##$aTT898.2$hHandicrafts. Arts and crafts$hHome arts. Homecrafts$hDecorative crafts$hFancy articles$jMerry-go-round art |
| 553 |
0#$wl$aNK5030$cNK5035$hDecorative arts. Applied arts. Decoration and ornament$hOther arts and art industries$jFairground art$tHandicraft of carousel horses |
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Cross reference display example at NK5030-NK5035:
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| Decorative arts. Applied arts. Decoration and ornament |
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Other arts and industries |
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Fairground art |
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Cf. TT898.2, Handicraft of carousel horses |
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| 084 |
0#$addc$c21 [Dewey Decimal Classification] |
| 153 |
##$a546.8$hNatural sciences and mathematics$hChemistry and allied sciences$kChemistry$hInorganic chemistry$jPeriodic table |
| 553 |
0#$wk$a541.24$hNatural sciences and mathematics$hChemistry and allied sciences$kChemistry$kGeneral topics in chemistry$hPhysical and theoretical chemistry$hTheoretical chemistry$jAtomic structure$tperiodic table |
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Cross reference display example at 541.24:
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| 541.24 Atomic structure |
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Class periodic table in 546.8 |
$w - Control subfield Four fixed-position character positions (designated as $w/0,
$w/1, $w/2, and $w/3) that indicate whether
special instructions apply to the display of the 453 or 553 classification number,
whether the reference should be displayed, and whether a field 685 (History Note)
is associated with the tracing. Because the definitions of the codes in subfield
$w are dependent on the character position in which they occur, the
coding of any character position mandates that each preceding character position
contains a code or fill character (|); succeeding character positions need not be
used. For example, if subfield $w/1 (Hierarchical relationship) is not
applicable, but $w/3 (History reference) is, subfield $w/1
must contain code n (Not applicable), and subfield $w/2 must contain
either a code or a fill character. If $w/1, $w/2, and
$w/3 are not applicable, only $w/0 need be coded.
/0 - Special relationship One-character alphabetic code that describes a relationship between the
classification numbers contained in field 153 and fields 453 or 553. The codes
may be used to generate a special reference instruction phrase in a cross
reference display. If more than one code is applicable, the field may be
repeated and the generation of a display of one of the tracings may be
suppressed by code a (Reference not displayed) in subfield $w/2
(Reference display).
| a - Previous classification number |
k - Class elsewhere reference |
| b - New classification number |
l - See also reference |
| i - Reference instruction phrase in $i |
m - Standard subdivisions do-not-use reference |
| j - See reference |
n - Not applicable |
a - Previous classification number Classification number in the tracing field is a number previously used for
the subject. It directs the user to the currently used number in field 153
(Classification Number). The code may be used to generate a special
reference instruction phrase such as
see also under the new number:
in a cross reference display. Field 685 (History Note) may be included in
the record to give additional information about the history of the
classification number contained in the tracing.
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| 084 |
0#$addc$c22 [Dewey Decimal Classification]
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| 153 |
##$a332.45$hSocial sciences$hEconomics$hFinancial economics$hMoney$jForeign exchange |
| 453 |
0#$wahna$a332.454$hSocial sciences$hEconomics$hFinancial economics$hMoney$hForeign exchange$jForeign exchange with a paper
standard
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| 685 |
12$iNumber discontinued; class in$a332.45$d2003$222 |
b - New classification number Number in the tracing field entirely supersedes the number contained in
field 153. The code may be used to generate a special reference instruction
phrase such as
see also under the previous number: in a cross
reference display. If the meaning of the number in field 153 is changed only
for
certain subjects, this complex information is conveyed in field
685 (History Note). This type of reference might be used by a library that
assigns new classification numbers to new books but does not reclassify
existing ones when a new edition is published.
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| 084 |
0#$addc$c19 [Dewey Decimal Classification]
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| 153 |
##$a787.1$hThe arts. Fine and decorative arts$hMusic$kIndividual mediums of musical expression$kInstruments and instrumental music$kSpecific instruments and their music$kOther instruments and their music$hString instruments and their music$kSpecific bowed instruments and their music$jViolin |
| 553 |
0#$wbnna$a787.2$hThe arts. Fine and decorative arts$hMusic$kInstruments and their music$kSpecific instruments and their music$hStringed instruments (Chordophones). Bowed string
instruments$jViolins
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Cross reference display at 787.2:
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See also under the previous number: 787.1 |
i - Reference instruction phrase in subfield $i Used in conjunction with subfield $i (Reference instruction
phrase) when explicit text is needed that does not fall into any other
category.
j - See reference Number in the tracing field is a simple see reference that guides the user
from the number(s) in the tracing field (field 453 or 553) to the number(s)
in field 153 (Classification Number). The code may be used to generate a
special reference instruction phrase such as
see or
For [topic]
see [number].
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| 084 |
0#$alcc [Library of Congress Classification]
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| 153 |
##$zP-PZ1$a499$hTable for languages (900 nos.)$hTranslating$jMachine translating |
| 553 |
1#$wj$zP-PZ1$a691$hTable for languages$hLexicography$hDictionaries$hOther special lists$jWord frequency lists$tResearch on word frequency, etc., in connection
with machine translating
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| 680 |
#0$iIncluding research |
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Cross reference display example at 691, Table I, P-PZ:
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| Table for languages (900 nos.) |
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Lexicography |
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Dictionaries |
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Other special lists |
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Word frequency lists |
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Research on word frequency, etc., in connection with machine
translating, |
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see P-PZ, Table I, 499
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| 084 |
0#$addc$c22 [Dewey Decimal Classification]
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| 153 |
##$a621.45$hTechnology (Applied sciences)$hEngineering and allied operations$hApplied physics$hPrime movers and heat engineering$jWind engines |
| 553 |
0#$wjg$a621.42$hTechnology (Applied sciences)$hEngineering and allied operations$hApplied physics$hPrime movers and heat engineering$jStirling engines and air motors |
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Cross reference display example at 621.42:
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| 621.42 Stirling engines and air
motors
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For wind engines, see 621.45 |
k - Class elsewhere reference [553 only]
Topic in subfield $t (Topic) of the tracing field is classed in
another number that is not a subdivision of the number in subfield
$a (Classification number element-Single number or beginning
number of span) of field 553. The code may be used to generate a special
instruction phrase such as
Class [topic] in [number].
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| 084 |
0#$addc$c22 [Dewey Decimal Classification] |
| 153 |
##$a331.23$hSocial sciences$hEconomics$kEconomics of labor, finance, land, energy$hLabor economics$hConditions of employment$jGuaranteed-wage plans |
| 553 |
0#$wk$a331.2162$hSocial sciences$hEconomics$kEconomics of labor, finance, land, energy$hLabor economics$hConditions of employment$hCompensation$hMethods of compensation$tTime payments |
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Cross reference display example at 331.2162:
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| Class Guaranteed-wage plans in 331.23 |
l - See also reference [553 only]
Number in the tracing field guides the user from the number(s) in field 553
to related topics classed in the number(s) in field 153. The code may be
used to generate a special instruction phrase such as
Cf. [number]
[topic] or
see also [number] for [topic].
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| 084 |
0#$addc$c22 [Dewey Decimal Classification]
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| 153 |
##$a305.562$hSocial sciences$kSpecific topics in sociology and anthropology$hSocial groups$hSocial classes$hLower, alienated, excluded classes$jWorking class |
| 553 |
0#$wl$a331$hSocial sciences$hEconomics$kEconomics of labor, finance, land, energy$jLabor economics$tsociology of working class |
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| 084 |
0#$addc$c22 [Dewey Decimal Classification]
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| 153 |
##$a306.36$hSocial sciences$kSpecific topics in sociology and anthropology$hCulture and institutions$kCultural institutions$hEconomic institutions$jSystems of labor |
| 553 |
0#$wl$a331$hSocial sciences$hEconomics$kEconomics of labor, finance, land, energy$jLabor economics$tsociology of labor |
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Cross reference display example at 331:
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| See also 305.562 for sociology of working class; also 306.36 for
sociology of labor
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m - Standard subdivisions do-not-use reference One or more standard subdivisions may not be used with the number in the
tracing field. The code may be used to generate a special instruction phrase
such as
Do not use for [topic]; class in [number].
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| 084 |
0#$addc$c22 [Dewey Decimal Classification]
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| 153 |
##$a331.01$hSocial sciences$hEconomics$kEconomics of labor, finance, land, energy$hLabor economics$jPhilosophy and theory |
| 553 |
0#$wmh$a331.011$hSocial sciences$hEconomics$kEconomics of labor, finance, land, energy$hLabor economics$hPhilosophy and theory$jRights and position of labor$tsystems analysis applied to labor
economics
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Cross reference display example at 331.011:
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| Do not use for systems analysis applied to labor economics; class in
331.01
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n - Not applicable Relationship between the heading in the tracing field and the 153 heading is
not one of the special relationships for which other codes are defined in
subfield $w/0. A tag related reference instruction phrase such as
see or see also may be used in a cross reference
display from the related heading. If code n is applicable, subfield
$w need not be coded unless a subsequent character position is
required.
/1 - Hierarchical relationship One-character alphabetic code which indicates the nature of the hierarchy when
the tracing is for a hierarchical relationship between topics. The codes may be
used to generate a special instruction phrase in a cross reference display.
| g - Number representing broader topic |
| h - Number representing narrower topic |
| n - Not applicable |
g - Number representing broader topic Number in the tracing field represents a broader topic than the number at
the preceding level of the caption hierarchy that is contained in field 153
(Classification Number). The code may be used to generate a special
reference instruction phrase such as
see also under the narrower
number: in a cross reference display.
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| 084 |
0#$addc$c21 [Dewey Decimal Classification]
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| 153 |
##$a621.252$hTechnology (Applied sciences)$hEngineering and allied operations$hApplied physics$kFluid-power technologies$hHydraulic-power technology$hPumps and accumulators$jPumps |
| 553 |
0#$wjg$a621.69$hTechnology (Applied sciences)$hEngineering and allied operations$hApplied physics$hBlowers, fans, pumps$kPumps$jPumps. Pneumatic pumps$thydraulic pumps |
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| 084 |
0#$addc$c21 [Dewey Decimal Classification]
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| 153 |
##$a621.64$hTechnology (Applied sciences)$hEngineering and allied operations$hApplied physics$hBlowers, fans, pumps$kPumps$jHand pumps |
| 553 |
0#$wjg$a621.69$hTechnology (Applied sciences)$hEngineering and allied operations$hApplied physics$hBlowers, fans, pumps$kPumps$jPumps. Pneumatic pumps$thand pumps |
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| 084 |
0#$addc$c21 [Dewey Decimal Classification]
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| 153 |
##$a621.65$hTechnology (Applied sciences)$hEngineering and allied operations$hApplied physics$hBlowers, fans, pumps$kPumps$jReciprocating pumps |
| 553 |
0#$wjg$a621.69$hTechnology (Applied sciences)$hEngineering and allied operations$hApplied physics$hBlowers, fans, pumps$kPumps$jPumps. Pneumatic pumps$treciprocating pumps |
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| 084 |
0#$addc$c21 [Dewey Decimal Classification]
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| 153 |
##$a621.66$hTechnology (Applied sciences)$hEngineering and allied operations$hApplied physics$hBlowers, fans, pumps$kPumps$jRotary pumps |
| 553 |
0#$wjg$a621.69$hTechnology (Applied sciences)$hEngineering and allied operations$hApplied physics$hBlowers, fans, pumps$kPumps$jPumps. Pneumatic pumps$trotary pumps |
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| 084 |
0#$addc$c21 [Dewey Decimal Classification]
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| 153 |
##$a621.67$hTechnology (Applied sciences)$hEngineering and allied operations$hApplied physics$hBlowers, fans, pumps$kPumps$jCentrifugal pumps |
| 553 |
0#$wjg$a621.69$hTechnology (Applied sciences)$hEngineering and allied operations$hApplied physics$hBlowers, fans, pumps$kPumps$jPumps. Pneumatic pumps$tcentrifugal pumps |
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Cross reference display at 621.69:
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| For hydraulic pumps, see 621.252; for hand pumps, see 621.64; for
reciprocating pumps, see 621.65; for rotary pumps, see 621.66; for
centrifugal pumps, see 621.67
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| [In this example, subfield $w/0 controls the display, which
is for a see reference.]
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h - Number representing narrower topic Number in the tracing field represents a narrower topic than the number at
the lower level of the caption hierarchy that is contained in field 153. The
code may be used to generate a special reference instruction phrase such as
see also under the broader number: in a cross reference
display.
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| 084 |
0#$addc$c22 [Dewey Decimal Classification]
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| 153 |
##$a666.3$hTechnology (Applied sciences)$hChemical engineering and related technologies$hCeramic and allied technologies$jPottery |
| 553 |
0#$wkh$a666.5$c666.6$hTechnology (Applied sciences)$hChemical engineering and related technologies$hCeramic and allied technologies$jSpecific types of pottery$tcomprehensive works |
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Cross reference display at 666.5-666.6:
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| Class comprehensive works in 666.3 |
| [In this example subfield $w/0 controls the
display.] |
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n - Not applicable A hierarchical relationship is not applicable to the tracing. If code n is
applicable, subfield $w/1 need not be coded unless a subsequent
character position is required.
/2 - Reference display One-character alphabetic code that enables the generation or suppression of a
cross reference from a 453 or 553 field.
| a - Reference not displayed |
| n - Not applicable |
a - Reference not displayed Generation of a cross reference display from a tracing field should be
suppressed. Code a is used when a 253 or 353 complex reference field
contains the reference to be displayed or when it is otherwise not desirable
to display the reference.
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| 084 |
0#$addc$c22 [Dewey Decimal Classification]
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| 153 |
##$a230$c270$hReligion$kChristianity$jSpecific elements of Christianity |
| 553 |
0#$wnga$a230$c280$hReligion$jChristianity
[The 553 field contains a tracing from a DDC centered entry, or
broader number span, which facilitates online browsing.] |
n - Not applicable There is no reference display restriction on the tracing field. If code n is
applicable, subfield $w/2 need not be coded unless
$w/3 is used.
/3 - History reference One-character alphabetic code that indicates whether field 685 (History Note)
in a record refers to the number in a 453 or 553 tracing.
| a - History reference, field 685 used |
| n - Not applicable |
a - History reference, field 685 used Record contains a field 685 that contains further information about the
number in the 453 or 553 tracing field.
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| 084 |
0#$addc$c21 [Dewey Decimal Classification]
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| 153 |
##$z2$a71334$hGeographic Areas, Historical Periods, Persons$kSpecific continents, countries, localities;
extraterrestrial worlds$kThe modern world; extraterrestrial worlds$hNorth America$hCanada$hOntario$kSouthern Ontario$hLake Erie region$jElgin County
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1#$wanna$z2$a71335$hGeographic Areas, Historical Periods, Persons$kSpecific continents, countries, localities;
extraterrestrial worlds$kThe modern world; extraterrestrial worlds$hNorth America$hCanada$hOntario$kSouthern Ontario$hLake Erie region$jSt. Thomas
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10$iRelocated to$z2$a71334$d19960930$221 |
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Cross reference display at T2-71335:
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| --[71335] St. Thomas |
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See the new number: T2-71335 |
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Relocated to -71335 |
| [If desired the tracing may be suppressed for display purposes. The
second note about relocation is generated from field 685 (History
Note).] |
n - Not applicable Either that the record does not contain field 685 (History Note) or that
field 685 refers to the classification number contained in field 153. If
code n is applicable, subfield $w/3 need not be coded.
■ REFERENCE FIELDS-COMPLEX CROSS REFERENCES
Complex cross references are carried directly in records as reference note fields.
They are used when relationships exist between classification numbers that cannot be
adequately conveyed by one or more simple cross references generated from 453 or 553
tracings. Subfield $i (Explanatory text) contains textual information in
field 253 (Complex See Reference) or field 353 (Complex See Also Reference).
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b [table record] |
| 084 |
0#$alcc [Library of Congress Classification] |
| 153 |
##$zKF1$a7.5$c7.529$hTable of form divisions (20 nos.)$hStatutes. Regulations. Rules of practice$hFederal legislation$hRegulations. Rules of practice$jParticular regulations or rules of practice (or groups of
regulations or rules adopted as a whole)
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| 253 |
0#$iFor rules of practice before a separately classed agency,
see the issuing agency
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INPUT CONVENTIONS
Tracing Fields - General input conventions for the 453 and 553 tracing fields are provided in the X53
Classification Numbers-General Information section. The input conventions for
the Reference fields are provided in the description of each field.
Display Constants for Cross References - In the 453 and 553 tracing fields, reference instruction phrases such as those listed
below are not carried in the MARC record. They may be system generated as display
constants associated with the field tag. In complex reference fields 253 and 353, the
complete reference instruction may be a combination of a tag-related phrase, such as
see: or
see also: and explicit text in subfield $i.
| Tag-related: |
| see: |
| see also: |
In complex reference fields 253 and 353, the complete reference instruction may be a
combination of a tag-related phrase, such as
see: or
see also: and
explicit text in subfield $i
SCHEME-SPECIFIC CONVENTIONS
General Conventions - General scheme specific conventions for the 453 and 553 tracing fields are provided in
the X53 Classification Numbers-General Information section. The scheme-specific
conventions for the Reference fields (253, 353) are provided in the description of each
field. The Library of Congress Classification scheme does not use subfield
$t in field 453.
Display Constants for Cross References - In the 453 and 553 tracing fields, reference instruction phrases such as those listed
below are not carried in the MARC record. The following display constants may be system
generated by the code in subfield $w/0 (Special relationship) and the code in
field 084 (Classification Scheme and Edition).
| Code |
Name |
DDC |
LCC |
| a |
Previous number |
undetermined |
undetermined |
| b |
New number |
undetermined |
undetermined |
| j |
See |
For topic see number |
topic see number |
| k |
Class elsewhere |
Class topic in number |
not applicable |
| l |
See also |
See also number for topic |
Cf. number topic |
| m |
Standard subdivision |
Do not use for topic; class in number |
not applicable |
The following display constants may be system generated by the code in subfield
$w/1 (Hierarchical relationship).
| Code |
Name |
DDC |
LCC |
| g |
Number representing broader topic |
see also under narrower number |
undetermined |
| h |
Number representing narrower topic |
see also under the broader number |
undetermined |