.ig
Copyright (C) 1989-2000, 2001, 2002, 2003, 2004, 2005
  Free Software Foundation, Inc.

Permission is granted to make and distribute verbatim copies of
this manual provided the copyright notice and this permission notice
are preserved on all copies.

Permission is granted to copy and distribute modified versions of this
manual under the conditions for verbatim copying, provided that the
entire resulting derived work is distributed under the terms of a
permission notice identical to this one.

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manual into another language, under the above conditions for modified
versions, except that this permission notice may be included in
translations approved by the Free Software Foundation instead of in
the original English.
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.\" the current line-length - indent, use the default indent.
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.\" The BSD man macros can't handle " in arguments to font change macros,
.\" so use \(ts instead of ".
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.
.
.TH @G@REFER @MAN1EXT@ "@MDATE@" "Groff Version @VERSION@"
.
.
.
.SH NAME
@g@refer \- preprocess bibliographic references for groff
.
.
.
.SH SYNOPSIS
.nr a \n(.j
.ad l
.nr i \n(.i
.in +\w'\fB@g@refer 'u
.ti \niu
.B @g@refer
.
.de OP
.  ie \\n(.$-1 .RI "[\ \fB\\$1\fP" "\\$2" "\ ]"
.  el .RB "[\ " "\\$1" "\ ]"
..
.
.OP \-benvCPRS
.OP \-a n
.OP \-c fields
.OP \-f n
.OP \-i fields
.OP \-k field
.OP \-l m,n
.OP \-p \%filename
.OP \-s fields
.OP \-t n
.OP \-B field.macro
.RI [\  \%filename \|.\|.\|.\ ]
.br
.ad \na
.
.LP
It is possible to have whitespace between a command line option and its
parameter.
.
.
.
.SH DESCRIPTION
This file documents the GNU version of
.BR refer ,
which is part of the groff document formatting system.
.B refer
copies the contents of
.IR filename \|.\|.\|.\&
to the standard output,
except that lines between
.B .[
and
.B .]\&
are interpreted as citations,
and lines between
.B .R1
and
.B .R2
are interpreted as commands about how citations are to be processed.
.
.LP
Each citation specifies a reference.
The citation can specify a reference that is contained in
a bibliographic database by giving a set of keywords
that only that reference contains.
Alternatively it can specify a reference by supplying a database
record in the citation.
A combination of these alternatives is also possible.
.
.LP
For each citation,
.B refer
can produce a mark in the text.
This mark consists of some label which can be separated from
the text and from other labels in various ways.
For each reference it also outputs
.B groff
commands that can be used by a macro package to produce a formatted
reference for each citation.
The output of
.B refer
must therefore be processed using a suitable macro package.
The
.B \-ms
and
.B \-me
macros are both suitable.
The commands to format a citation's reference can be output immediately after
the citation,
or the references may be accumulated,
and the commands output at some later point.
If the references are accumulated, then multiple citations of the same
reference will produce a single formatted reference.
.
.LP
The interpretation of lines between
.B .R1
and
.B .R2
as commands is a new feature of GNU
.BR refer .
Documents making use of this feature can still be processed by
Unix refer just by adding the lines
.
.RS
.LP
.nf
.ft B
\&.de R1
\&.ig R2
\&..
.ft
.fi
.RE
.
to the beginning of the document.
This will cause
.B troff
to ignore everything between
.B .R1
and
.BR .R2 .
The effect of some commands can also be achieved by options.
These options are supported mainly for compatibility with Unix refer.
It is usually more convenient to use commands.
.
.LP
.B refer
generates
.B .lf
lines so that filenames and line numbers in messages produced
by commands that read
.B refer
output will be correct;
it also interprets lines beginning with
.B .lf
so that filenames and line numbers in the messages and
.B .lf
lines that it produces will be accurate even if the input has been
preprocessed by a command such as
.BR @g@soelim (@MAN1EXT@).
.
.
.
.SH OPTIONS
.
.LP
Most options are equivalent to commands
(for a description of these commands see the
.B Commands
subsection):
.
.nr a \n(.j
.ad l
.TP
.B \-b
.B "no-label-in-text; no-label-in-reference"
.
.TP
.B \-e
.B accumulate
.
.TP
.B \-n
.B no-default-database
.
.TP
.B \-C
.B compatible
.
.TP
.B \-P
.B move-punctuation
.
.TP
.B \-S
.B
label\ "(A.n|Q)\ ',\ '\ (D.y|D)"; \%bracket-label\ "\ ("\ )\ ";\ "
.
.TP
.BI \-a n
.B reverse
.BI A n
.
.TP
.BI \-c fields
.B capitalize
.I fields
.
.TP
.BI \-f n
.B label
.BI % n
.
.TP
.BI \-i fields
.B search-ignore
.I fields
.
.TP
.B \-k
.B label
.B L\(ti%a
.
.TP
.BI \-k field
.B label
.IB field \(ti%a
.
.TP
.B \-l
.B label
.BI A.nD.y%a
.
.TP
.BI \-l m
.B label
.BI A.n+ m D.y%a
.
.TP
.BI \-l, n
.B label
.BI A.nD.y\- n %a
.
.TP
.BI \-l m , n
.B label
.BI A.n+ m D.y\- n %a
.
.TP
.BI \-p filename
.B database
.I filename
.
.TP
.BI \-s spec
.B sort
.I spec
.
.TP
.BI \-t n
.B search-truncate
.I n
.ad \na
.
.LP
These options are equivalent to the following commands with the
addition that the filenames specified on the command line are
processed as if they were arguments to the
.B bibliography
command instead of in the normal way:
.
.TP
.B \-B
.B "annotate X AP; no-label-in-reference"
.
.TP
.BI \-B field . macro
.B annotate
.I field
.IB macro ;
.B no-label-in-reference
.
.LP
The following options have no equivalent commands:
.
.TP
.B \-v
Print the version number.
.
.TP
.B \-R
Don't recognize lines beginning with
.BR .R1 / .R2 .
.
.
.
.SH USAGE
.
.
.SS Bibliographic databases
The bibliographic database is a text file consisting of records
separated by one or more blank lines.
Within each record fields start with a
.B %
at the beginning of a line.
Each field has a one character name that immediately follows the
.BR % .
It is best to use only upper and lower case letters for the names
of fields.
The name of the field should be followed by exactly one space,
and then by the contents of the field.
Empty fields are ignored.
The conventional meaning of each field is as follows:
.
.TP
.B A
The name of an author.
If the name contains a title such as
.B Jr.\&
at the end,
it should be separated from the last name by a comma.
There can be multiple occurrences of the
.B A
field.
The order is significant.
It is a good idea always to supply an
.B A
field or a
.B Q
field.
.
.TP
.B B
For an article that is part of a book, the title of the book.
.
.TP
.B C
The place (city) of publication.
.
.TP
.B D
The date of publication.
The year should be specified in full.
If the month is specified, the name rather than the number of the month
should be used, but only the first three letters are required.
It is a good idea always to supply a
.B D
field;
if the date is unknown, a value such as
.B in press
or
.B unknown
can be used.
.
.TP
.B E
For an article that is part of a book, the name of an editor of the book.
Where the work has editors and no authors,
the names of the editors should be given as
.B A
fields and
.B ,\ (ed)
or
.B ,\ (eds)
should be appended to the last author.
.
.TP
.B G
US Government ordering number.
.
.TP
.B I
The publisher (issuer).
.
.TP
.B J
For an article in a journal, the name of the journal.
.
.TP
.B K
Keywords to be used for searching.
.
.TP
.B L
Label.
.
.TP
.B N
Journal issue number.
.
.TP
.B O
Other information.
This is usually printed at the end of the reference.
.
.TP
.B P
Page number.
A range of pages can be specified as
.IB m \- n\fR.
.
.TP
.B Q
The name of the author, if the author is not a person.
This will only be used if there are no
.B A
fields.
There can only be one
.B Q
field.
.
.TP
.B R
Technical report number.
.
.TP
.B S
Series name.
.
.TP
.B T
Title.
For an article in a book or journal,
this should be the title of the article.
.
.TP
.B V
Volume number of the journal or book.
.
.TP
.B X
Annotation.
.
.LP
For all fields except
.B A
and
.BR E ,
if there is more than one occurrence of a particular field in a record,
only the last such field will be used.
.
.LP
If accent strings are used, they should follow the character to be accented.
This means that the
.B AM
macro must be used with the
.B \-ms
macros.
Accent strings should not be quoted:
use one
.B \e
rather than two.
.
.
.SS Citations
The format of a citation is
.
.RS
.BI .[ opening-text
.br
.I "flags keywords"
.br
.I fields
.br
.BI .] closing-text
.RE
.
.LP
The
.IR opening-text ,
.IR closing-text
and
.I flags
components are optional.
Only one of the
.I keywords
and
.I fields
components need be specified.
.
.LP
The
.I keywords
component says to search the bibliographic databases for a reference
that contains all the words in
.IR keywords .
It is an error if more than one reference if found.
.
.LP
The
.I fields
components specifies additional fields to replace or supplement
those specified in the reference.
When references are being accumulated and the
.I keywords
component is non-empty,
then additional fields should be specified only on the first
occasion that a particular reference is cited,
and will apply to all citations of that reference.
.
.LP
The
.I opening-text
and
.I closing-text
component specifies strings to be used to bracket the label instead
of the strings specified in the
.B bracket-label
command.
If either of these components is non-empty,
the strings specified in the
.B bracket-label
command will not be used;
this behaviour can be altered using the
.B [
and
.B ]
flags.
Note that leading and trailing spaces are significant for these components.
.
.LP
The
.I flags
component is a list of
non-alphanumeric characters each of which modifies the treatment
of this particular citation.
Unix refer will treat these flags as part of the keywords and
so will ignore them since they are non-alphanumeric.
The following flags are currently recognized:
.
.TP
.B #
This says to use the label specified by the
.B short-label
command,
instead of that specified by the
.B label
command.
If no short label has been specified, the normal label will be used.
Typically the short label is used with author-date labels
and consists of only the date and possibly a disambiguating letter;
the
.B #
is supposed to be suggestive of a numeric type of label.
.
.TP
.B [
Precede
.I opening-text
with the first string specified in the
.B bracket-label
command.
.
.TP
.B ]
Follow
.I closing-text
with the second string specified in the
.B bracket-label
command.
.
.LP
One advantages of using the
.B [
and
.B ]
flags rather than including the brackets in
.I opening-text
and
.I closing-text
is that
you can change the style of bracket used in the document just by changing the
.B bracket-label
command.
Another advantage is that sorting and merging of citations
will not necessarily be inhibited if the flags are used.
.
.LP
If a label is to be inserted into the text,
it will be attached to the line preceding the
.B .[
line.
If there is no such line, then an extra line will be inserted before the
.B .[
line and a warning will be given.
.
.LP
There is no special notation for making a citation to multiple references.
Just use a sequence of citations, one for each reference.
Don't put anything between the citations.
The labels for all the citations will be attached to the line preceding
the first citation.
The labels may also be sorted or merged.
See the description of the
.B <>
label expression, and of the
.B sort-adjacent-labels
and
.B abbreviate-label-ranges
command.
A label will not be merged if its citation has a non-empty
.I opening-text
or
.IR closing-text .
However, the labels for a citation using the
.B ]
flag and without any
.I closing-text
immediately followed by a citation using the
.B [
flag and without any
.I opening-text
may be sorted and merged
even though the first citation's
.I opening-text
or the second citation's
.I closing-text
is non-empty.
(If you wish to prevent this just make the first citation's
.I closing-text
.BR \e& .)
.
.
.SS Commands
Commands are contained between lines starting with
.B .R1
and
.BR .R2 .
Recognition of these lines can be prevented by the
.B \-R
option.
When a
.B .R1
line is recognized any accumulated references are flushed out.
Neither
.B .R1
nor
.B .R2
lines,
nor anything between them
is output.
.
.LP
Commands are separated by newlines or
.BR ; s.
.B #
introduces a comment that extends to the end of the line
(but does not conceal the newline).
Each command is broken up into words.
Words are separated by spaces or tabs.
A word that begins with
.B \(ts
extends to the next
.B \(ts
that is not followed by another
.BR \(ts .
If there is no such
.B \(ts
the word extends to the end of the line.
Pairs of
.B \(ts
in a word beginning with
.B \(ts
collapse to a single
.BR \(ts .
Neither
.B #
nor
.B ;
are recognized inside
.BR \(ts s.
A line can be continued by ending it with
.BR \e ;
this works everywhere except after a
.BR # .
.
.LP
.ds n \fR*
Each command
.I name
that is marked with \*n has an associated negative command
.BI no- name
that undoes the effect of
.IR name .
For example, the
.B no-sort
command specifies that references should not be sorted.
The negative commands take no arguments.
.
.LP
In the following description each argument must be a single word;
.I field
is used for a single upper or lower case letter naming a field;
.I fields
is used for a sequence of such letters;
.I m
and
.I n
are used for a non-negative numbers;
.I string
is used for an arbitrary string;
.I filename
is used for the name of a file.
.
.Tp \w'\fBabbreviate-label-ranges'u+2n
.BI abbreviate\*n\  fields\ string1\ string2\ string3\ string4
Abbreviate the first names of
.IR fields .
An initial letter will be separated from another initial letter by
.IR string1 ,
from the last name by
.IR string2 ,
and from anything else
(such as a
.B von
or
.BR de )
by
.IR string3 .
These default to a period followed by a space.
In a hyphenated first name,
the initial of the first part of the name will be separated from the hyphen by
.IR string4 ;
this defaults to a period.
No attempt is made to handle any ambiguities that might
result from abbreviation.
Names are abbreviated before sorting and before
label construction.
.
.TP
.BI abbreviate-label-ranges\*n\  string
Three or more adjacent labels that refer to consecutive references
will be abbreviated to a label consisting
of the first label, followed by
.I string
followed by the last label.
This is mainly useful with numeric labels.
If
.I string
is omitted it defaults to
.BR \- .
.
.TP
.B accumulate\*n
Accumulate references instead of writing out each reference
as it is encountered.
Accumulated references will be written out whenever a reference
of the form
.
.RS
.IP
.B .[
.br
.B $LIST$
.br
.B .]
.
.LP
is encountered,
after all input files hve been processed,
and whenever
.B .R1
line is recognized.
.RE
.
.TP
.BI annotate\*n\  field\ string
.I field
is an annotation;
print it at the end of the reference as a paragraph preceded by the line
.
.RS
.IP
.BI . string
.
.LP
If
.I macro
is omitted it will default to
.BR AP ;
if
.I field
is also omitted it will default to
.BR X .
Only one field can be an annotation.
.RE
.
.TP
.BI articles\  string \fR\|.\|.\|.
.IR string \|.\|.\|.\&
are definite or indefinite articles, and should be ignored at the beginning of
.B T
fields when sorting.
Initially,
.BR the ,
.B a
and
.B an
are recognized as articles.
.
.TP
.BI bibliography\  filename \fR\|.\|.\|.
Write out all the references contained in the bibliographic databases
.IR filename \|.\|.\|.
This command should come last in a
.BR .R1 / .R2
block.
.
.TP
.BI bracket-label\  string1\ string2\ string3
In the text, bracket each label
with
.I string1
and
.IR string2 .
An occurrence of
.I string2
immediately followed by
.I string1
will be turned into
.IR string3 .
The default behaviour is
.
.RS
.IP
.B
bracket-label \e*([. \e*(.] ", "
.RE
.
.TP
.BI capitalize\  fields
Convert
.I fields
to caps and small caps.
.
.TP
.B compatible\*n
Recognize
.B .R1
and
.B .R2
even when followed by a character other than space or newline.
.
.TP
.BI database\  filename \fR\|.\|.\|.
Search the bibliographic databases
.IR filename \|.\|.\|.
For each
.I filename
if an index
.IB filename @INDEX_SUFFIX@
created by
.BR @g@indxbib (@MAN1EXT@)
exists, then it will be searched instead;
each index can cover multiple databases.
.
.TP
.BI date-as-label\*n\  string
.I string
is a label expression that specifies a string with which to replace the
.B D
field after constructing the label.
See the
.B "Label expressions"
subsection for a description of label expressions.
This command is useful if you do not want explicit labels in the
reference list, but instead want to handle any necessary
disambiguation by qualifying the date in some way.
The label used in the text would typically be some combination of the
author and date.
In most cases you should also use the
.B no-label-in-reference
command.
For example,
.
.RS
.IP
.B "date-as-label D.+yD.y%a*D.-y"
.
.LP
would attach a disambiguating letter to the year part of the
.B D
field in the reference.
.RE
.
.TP
.B default-database\*n
The default database should be searched.
This is the default behaviour, so the negative version of
this command is more useful.
.B refer
determines whether the default database should be searched
on the first occasion that it needs to do a search.
Thus a
.B no-default-database
command must be given before then,
in order to be effective.
.
.TP
.BI discard\*n\  fields
When the reference is read,
.I fields
should be discarded;
no string definitions for
.I fields
will be output.
Initially,
.I fields
are
.BR XYZ .
.
.TP
.BI et-al\*n\  string\ m\ n
Control use of
.B "et al"
in the evaluation of
.B @
expressions in label expressions.
If the number of authors needed to make the author sequence
unambiguous is
.I u
and the total number of authors is
.I t
then the last
.IR t \|\-\| u
authors will be replaced by
.I string
provided that
.IR t \|\-\| u
is not less than
.I m
and
.I t
is not less than
.IR n .
The default behaviour is
.
.RS
.IP
.B
et-al " et al" 2 3
.RE
.
.TP
.BI include\  filename
Include
.I filename
and interpret the contents as commands.
.
.TP
.BI join-authors\  string1\ string2\ string3
This says how authors should be joined together.
When there are exactly two authors, they will be joined with
.IR string1 .
When there are more than two authors, all but the last two will
be joined with
.IR string2 ,
and the last two authors will be joined with
.IR string3 .
If
.I string3
is omitted,
it will default to
.IR string1 ;
if
.I string2
is also omitted it will also default to
.IR string1 .
For example,
.
.RS
.IP
.B
join-authors " and " ", " ", and "
.
.LP
will restore the default method for joining authors.
.RE
.
.TP
.B label-in-reference\*n
When outputting the reference,
define the string
.B [F
to be the reference's label.
This is the default behaviour; so the negative version
of this command is more useful.
.
.TP
.B label-in-text\*n
For each reference output a label in the text.
The label will be separated from the surrounding text as described in the
.B bracket-label
command.
This is the default behaviour; so the negative version
of this command is more useful.
.
.TP
.BI label\  string
.I string
is a label expression describing how to label each reference.
.
.TP
.BI separate-label-second-parts\  string
When merging two-part labels, separate the second part of the second
label from the first label with
.IR string .
See the description of the
.B <>
label expression.
.
.TP
.B move-punctuation\*n
In the text, move any punctuation at the end of line past the label.
It is usually a good idea to give this command unless you are using
superscripted numbers as labels.
.
.TP
.BI reverse\*n\  string
Reverse the fields whose names
are in
.IR string .
Each field name can be followed by a number which says
how many such fields should be reversed.
If no number is given for a field, all such fields will be reversed.
.
.TP
.BI search-ignore\*n\  fields
While searching for keys in databases for which no index exists,
ignore the contents of
.IR fields .
Initially, fields
.B XYZ
are ignored.
.
.TP
.BI search-truncate\*n\  n
Only require the first
.I n
characters of keys to be given.
In effect when searching for a given key
words in the database are truncated to the maximum of
.I n
and the length of the key.
Initially
.I n
is\ 6.
.
.TP
.BI short-label\*n\  string
.I string
is a label expression that specifies an alternative (usually shorter)
style of label.
This is used when the
.B #
flag is given in the citation.
When using author-date style labels, the identity of the author
or authors is sometimes clear from the context, and so it
may be desirable to omit the author or authors from the label.
The
.B short-label
command will typically be used to specify a label containing just
a date and possibly a disambiguating letter.
.
.TP
.BI sort\*n\  string
Sort references according to
.BR string .
References will automatically be accumulated.
.I string
should be a list of field names, each followed by a number,
indicating how many fields with the name should be used for sorting.
.B +
can be used to indicate that all the fields with the name should be used.
Also
.B .\&
can be used to indicate the references should be sorted using the
(tentative) label.
(The
.B "Label expressions"
subsection describes the concept of a tentative label.)
.
.TP
.B sort-adjacent-labels\*n
Sort labels that are adjacent in the text according to their
position in the reference list.
This command should usually be given if the
.B abbreviate-label-ranges
command has been given,
or if the label expression contains a
.B <>
expression.
This will have no effect unless references are being accumulated.
.
.
.SS Label expressions
.
.LP
Label expressions can be evaluated both normally and tentatively.
The result of normal evaluation is used for output.
The result of tentative evaluation, called the
.IR "tentative label" ,
is used to gather the information
that normal evaluation needs to disambiguate the label.
Label expressions specified by the
.B date-as-label
and
.B short-label
commands are not evaluated tentatively.
Normal and tentative evaluation are the same for all types
of expression other than
.BR @ ,
.BR * ,
and
.B %
expressions.
The description below applies to normal evaluation,
except where otherwise specified.
.
.TP
.I field
.TQ
.I field\ n
The
.IR n -th
part of
.IR field .
If
.I n
is omitted, it defaults to\ 1.
.
.TP
.BI ' string '
The characters in
.I string
literally.
.
.TP
.B @
All the authors joined as specified by the
.B join-authors
command.
The whole of each author's name will be used.
However, if the references are sorted by author
(that is the sort specification starts with
.BR A+ ),
then authors' last names will be used instead, provided that this does
not introduce ambiguity,
and also an initial subsequence of the authors may be used
instead of all the authors, again provided that this does not
introduce ambiguity.
The use of only the last name for the
.IR i -th
author of some reference
is considered to be ambiguous if
there is some other reference,
such that the first
.IR i \|-\|1
authors of the references are the same,
the
.IR i -th
authors are not the same,
but the
.IR i -th
authors' last names are the same.
A proper initial subsequence of the sequence
of authors for some reference is considered to be ambiguous if there is
a reference with some other sequence of authors which also has
that subsequence as a proper initial subsequence.
When an initial subsequence of authors is used, the remaining
authors are replaced by the string specified by the
.B et-al
command;
this command may also specify additional requirements that must be
met before an initial subsequence can be used.
.B @
tentatively evaluates to a canonical representation of the authors,
such that authors that compare equally for sorting purpose
will have the same representation.
.
.TP
.BI % n
.TQ
.B %a
.TQ
.B %A
.TQ
.B %i
.TQ
.B %I
The serial number of the reference formatted according to the character
following the
.BR % .
The serial number of a reference is\ 1 plus the number of earlier references
with same tentative label as this reference.
These expressions tentatively evaluate to an empty string.
.
.TP
.IB expr *
If there is another reference with the same tentative label as
this reference, then
.IR expr ,
otherwise an empty string.
It tentatively evaluates to an empty string.
.
.TP
.IB expr + n
.TQ
.IB expr \- n
The first
.RB ( + )
or last
.RB ( \- )
.I n
upper or lower case letters or digits of
.IR expr .
Troff special characters (such as
.BR \e('a )
count as a single letter.
Accent strings are retained but do not count towards the total.
.
.TP
.IB expr .l
.I expr
converted to lowercase.
.
.TP
.IB expr .u
.I expr
converted to uppercase.
.
.TP
.IB expr .c
.I expr
converted to caps and small caps.
.
.TP
.IB expr .r
.I expr
reversed so that the last name is first.
.
.TP
.IB expr .a
.I expr
with first names abbreviated.
Note that fields specified in the
.B abbreviate
command are abbreviated before any labels are evaluated.
Thus
.B .a
is useful only when you want a field to be abbreviated in a label
but not in a reference.
.
.TP
.IB expr .y
The year part of
.IR expr .
.
.TP
.IB expr .+y
The part of
.I expr
before the year, or the whole of
.I expr
if it does not contain a year.
.
.TP
.IB expr .\-y
The part of
.I expr
after the year, or an empty string if
.I expr
does not contain a year.
.
.TP
.IB expr .n
The last name part of
.IR expr .
.
.TP
.IB expr1 \(ti expr2
.I expr1
except that if the last character of
.I expr1
is
.B \-
then it will be replaced by
.IR expr2 .
.
.TP
.I expr1\ expr2
The concatenation of
.I expr1
and
.IR expr2 .
.
.TP
.IB expr1 | expr2
If
.I expr1
is non-empty then
.I expr1
otherwise
.IR expr2 .
.
.TP
.IB expr1 & expr2
If
.I expr1
is non-empty
then
.I expr2
otherwise an empty string.
.
.TP
.IB expr1 ? expr2 : expr3
If
.I expr1
is non-empty
then
.I expr2
otherwise
.IR expr3 .
.
.TP
.BI < expr >
The label is in two parts, which are separated by
.IR expr .
Two adjacent two-part labels which have the same first part will be
merged by appending the second part of the second label onto the first
label separated by the string specified in the
.B separate-label-second-parts
command (initially, a comma followed by a space); the resulting label
will also be a two-part label with the same first part as before
merging, and so additional labels can be merged into it.
Note that it is permissible for the first part to be empty;
this maybe desirable for expressions used in the
.B short-label
command.
.
.TP
.BI ( expr )
The same as
.IR expr .
Used for grouping.
.
.LP
The above expressions are listed in order of precedence
(highest first);
.B &
and
.B |
have the same precedence.
.
.
.SS Macro interface
Each reference starts with a call to the macro
.BR ]- .
The string
.B [F
will be defined to be the label for this reference,
unless the
.B no-label-in-reference
command has been given.
There then follows a series of string definitions,
one for each field:
string
.BI [ X
corresponds to field
.IR X .
The number register
.B [P
is set to\ 1 if the
.B P
field contains a range of pages.
The
.BR [T ,
.B [A
and
.B [O
number registers are set to\ 1 according as the
.BR T ,
.B A
and
.B O
fields end with one of the characters
.BR .?! .
The
.B [E
number register will be set to\ 1 if the
.B [E
string contains more than one name.
The reference is followed by a call to the
.B ][
macro.
The first argument to this macro gives a number representing
the type of the reference.
If a reference contains a
.B J
field, it will be classified as type\ 1,
otherwise if it contains a
.B B
field, it will type\ 3,
otherwise if it contains a
.B G
or
.B R
field it will be type\ 4,
otherwise if contains a
.B I
field it will be type\ 2,
otherwise it will be type\ 0.
The second argument is a symbolic name for the type:
.BR other ,
.BR journal-article ,
.BR book ,
.B article-in-book
or
.BR tech-report .
Groups of references that have been accumulated
or are produced by the
.B bibliography
command are preceded by a call to the
.B ]<
macro and followed by a call to the
.B ]>
macro.
.
.
.
.SH FILES
.
.Tp \w'\fB@DEFAULT_INDEX@'u+2n
.B @DEFAULT_INDEX@
Default database.
.
.TP
.IB file @INDEX_SUFFIX@
Index files.
.
.
.
.SH ENVIRONMENT
.
.Tp \w'\fBREFER'u+2n
.B REFER
If set, overrides the default database.
.
.
.
.SH "SEE ALSO"
.BR @g@indxbib (@MAN1EXT@),
.BR @g@lookbib (@MAN1EXT@),
.BR lkbib (@MAN1EXT@)
.br
.
.
.
.SH BUGS
In label expressions,
.B <>
expressions are ignored inside
.BI . char
expressions.
.
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