Bibliographic records

A bibliographic record describes a referenced work in sufficient detail that it may be cited to accepted standards of scholarly and professional clarity. The record format permits annotation and extension that a document may use or ignore. A record is a plain text sequence of fields, one per line, each consisting of a percent sign %, an alphanumeric character classifying it, one space, and its contents. If a field's contents are empty, the field is ignored.

Frequently, such records are organized into a bibliographic database, with each entry separated by blank lines or file boundaries. This practice relieves documents of the need to maintain bibliographic data themselves. The programs glookbib(1) and lkbib(1) consult a bibliographic database, and gindxbib(1) indexes one to speed retrieval from it, reducing document processing time. Use of these tools is optional.

The conventional uses of the bibliographic field entries are as follows. Within a record, fields other than %A and %E replace previous occurrences thereof. The ordering of multiple %A and %E fields is significant.

%A

names an author. If the name contains a suffix such as “Jr.” or “III”, it should be separated from the surname by a comma. We recommend always supplying an %A field or a %Q field.

%B

records the title of the book within which a cited article is collected. See %J and %T.

%C

names the city or other place of publication.

%D

indicates the date of publication. Specify the year in full. If the month is specified, use its name rather than its number; only the first three letters are required. We recommend always supplying a %D field; if the date is unknown, use “in press” or “unknown” as its contents.

%E

names an editor of the book within which a cited article is collected. Where a work has editors but no authors, name the editors in %A fields and append “, (ed.)” or “, (eds.)” to the last of these.

%G

records the U.S. government ordering number, ISBN, DOI, or other unique identifier.

%I

names the publisher (issuer).

%J

records the name of the journal within which a cited article is collected. See %B and %T.

%K

lists keywords intended to aid searches.

%L

is a label; typically unused in database entries, it can override the label format otherwise determined.

%N

records the issue number of the journal within which a cited article is collected.

%O

presents additional (“other”) information, typically placed at the end of the reference.

%P

lists the page numbers of a cited work that is part of a larger collection. Specify a range with m-n.

%Q

names an institutional author when no %A fields are present. Only one %Q field is permitted.

%R

is an identifier for a report, thesis, memorandum, or other unpublished work.

%S

records the title of a series to which the cited work belongs.

%T

is the work's title. See %B and %J.

%V

is the volume number of the journal or book containing the cited work.

%X

is an annotation. By convention, it is not formatted in the citing document.

If the obsolescent “accent strings” feature of the ms or me macro packages is used, such strings should follow the character to be accented; an ms document must call the AM macro before using them. Do not quote accent strings: use one \ rather than two. See groff_char(7) for a modern approach to the problem of diacritics.

Citations

Citations have a characteristic format.

.[opening-text
flags keyword ...
field
...
.]closing-text

opening-text, closing-text, and flags are optional, and only one keyword or field need be specified. If keywords are present, grefer searches the bibliographic database(s) for a unique reference matching them. Multiple matches are an error; add more keywords to disambiguate the reference. In the absence of keywords, fields constitute the bibliographic record. Otherwise, fields specify additional data to replace or supplement those in the reference. When references are accumulating and keywords are present, specify additional fields at most on the first citation of a particular reference; they apply to all further citations thereof.

opening-text and closing-text are roff input used to bracket the label, overriding the bracket-label command. Leading and trailing spaces are significant. If either of these is non-empty, the corresponding argument to the bracket-label command is not used; alter this behavior with the [ and ] flags.

flags is a list of non-alphanumeric characters each of which modifies the treatment of the particular citation. AT&T refer ignores them since they are non-alphanumeric. They direct GNU refer as follows.

#

Use the label specified by the short-label command, if any. grefer otherwise uses the normal label. Typically, a short label implements author-date citation styles consisting of a name, a year, and a disambiguating letter if necessary. “#” is meant to suggest such a (quasi-)numeric label.

[

Precede opening-text with the first argument given to the bracket-label command.

]

Follow closing-text with the second argument given to the bracket-label command.

An advantage of the [ and ] flags over use of opening-text and closing-text is that you can update the document's bracketing style in one place using the bracket-label command. Another is that sorting and merging of citations is not necessarily inhibited if the flags are used.

grefer appends any label resulting from a citation to the roff input line preceding the .[ token. If there is no such line, grefer issues a warning diagnostic.

There is no special notation for citing multiple references in series. Use a sequence of citations, one for each reference, with nothing between them. grefer attaches all of their labels to the line preceding the first. These labels may be sorted or merged. See the description of the <> label expression, and of the sort-adjacent-labels and abbreviate-label-ranges commands. A label is not merged if its citation has a non-empty opening-text or closing-text. However, the labels for two adjacent citations, the former using the ] flag and without any closing-text, and the latter using the [ flag and without any opening-text, may be sorted and merged even if the former's opening-text or the latter's closing-text is non-empty. (To prevent these operations, use the dummy character escape sequence \& as the former's closing-text.)

Commands

Commands are contained between lines starting with .R1 and .R2. The -R option prevents recognition of these lines. When grefer encounters a .R1 line, it flushes any accumulated references. Neither .R1 nor .R2 lines, nor anything between them, is output.

Commands are separated by newlines or semicolons. A number sign (#) 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 a (neutral) double quote (") extends to the next double quote that is not followed by another double quote. If there is no such double quote, the word extends to the end of the line. Pairs of double quotes in a word beginning with a double quote collapse to one double quote. Neither a number sign nor a semicolon is recognized inside double quotes. A line can be continued by ending it with a backslash “\”; this works everywhere except after a number sign.

Each command name that is marked with * has an associated negative command no-name that undoes the effect of name. For example, the no-sort command specifies that references should not be sorted. The negative commands take no arguments.

In the following description each argument must be a single word; field is used for a single upper or lower case letter naming a field; fields is used for a sequence of such letters; m and n are used for a non-negative numbers; string is used for an arbitrary string; file is used for the name of a file.

abbreviate* fields string1 string2 string3 string4

Abbreviate the first names of fields. An initial letter will be separated from another initial letter by string1, from the surname by string2, and from anything else (such as “von” or “de”) by 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 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.

abbreviate-label-ranges* string

Three or more adjacent labels that refer to consecutive references will be abbreviated to a label consisting of the first label, followed by string, followed by the last label. This is mainly useful with numeric labels. If string is omitted, it defaults to “-”.

accumulate*

Accumulate references instead of writing out each reference as it is encountered. Accumulated references will be written out whenever a reference of the form

.[
$LIST$
.]

annotate* field string

field is an annotation; print it at the end of the reference as a paragraph preceded by the line

articles string ...

Each string is a definite or indefinite article, and should be ignored at the beginning of T fields when sorting. Initially, “a”, “an”, and “the” are recognized as articles.

bibliography file ...

Write out all the references contained in each bibliographic database file. This command should come last in an .R1/.R2 block.

bracket-label string1 string2 string3

In the text, bracket each label with string1 and string2. An occurrence of string2 immediately followed by string1 will be turned into string3. The default behavior is as follows.

bracket-label \*([. \*(.] ", "

capitalize fields

Convert fields to caps and small caps.

compatible*

Recognize .R1 and .R2 even when followed by a character other than space or newline.

database file ...

Search each bibliographic database file. For each file, if an index file.i created by gindxbib(1) exists, then it will be searched instead; each index can cover multiple databases.

date-as-label* string

string is a label expression that specifies a string with which to replace the D field after constructing the label. See subsection “Label expressions” below 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 no-label-in-reference command. For example,

date-as-label D.+yD.y%a*D.-y

default-database*

The default database should be searched. This is the default behavior, so the negative version of this command is more useful. grefer determines whether the default database should be searched on the first occasion that it needs to do a search. Thus a no-default-database command must be given before then, in order to be effective.

discard* fields

When the reference is read, fields should be discarded; no string definitions for fields will be output. Initially, fields are XYZ.

et-al* string m n

Configure use of “et al” in the evaluation of @ expressions in label expressions. If u is the number of authors needed to make the author sequence unambiguous and the total number of authors is t, then the last t-u authors will be replaced by string provided that t-u is not less than m and t is not less than n. The default behavior is as follows.

et-al " et al" 2 3

include file

Include file and interpret the contents as commands.

join-authors string1 string2 string3

Join multiple authors together with strings. When there are exactly two authors, they will be joined with string1. When there are more than two authors, all but the last two will be joined with string2, and the last two authors will be joined with string3. If string3 is omitted, it will default to string1; if string2 is also omitted it will also default to string1. For example,

join-authors " and " ", " ", and "

label-in-reference*

When outputting the reference, define the string [F to be the reference's label. This is the default behavior, so the negative version of this command is more useful.

label-in-text*

For each reference output a label in the text. The label will be separated from the surrounding text as described in the bracket-label command. This is the default behavior, so the negative version of this command is more useful.

label string

string is a label expression describing how to label each reference.

separate-label-second-parts string

When merging two-part labels, separate the second part of the second label from the first label with string. See the description of the <> label expression.

move-punctuation*

In the text, move any punctuation at the end of line past the label. We recommend employing this command unless you are using superscripted numbers as labels.

reverse* string

Reverse the fields whose names are in string. An optional integer after a field name limits the number of such fields to the given count; no integer means no limit.

search-ignore* fields

While searching for keys in databases for which no index exists, ignore the contents of fields. Initially, fields XYZ are ignored.

search-truncate* n

Only require the first 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 n and the length of the key. Initially, n is 6.

short-label* string

string is a label expression that specifies an alternative (usually shorter) style of label. This is used when the # 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 short-label command will typically be used to specify a label containing just a date and possibly a disambiguating letter.

sort* string

Sort references according to string. References will automatically be accumulated. 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. “+” can be used to indicate that all the fields with the name should be used. Also . can be used to indicate the references should be sorted using the (tentative) label. (Subsection “Label expressions” below describes the concept of a tentative label.)

sort-adjacent-labels*

Sort labels that are adjacent in the text according to their position in the reference list. This command should usually be given if the abbreviate-label-ranges command has been given, or if the label expression contains a <> expression. This has no effect unless references are being accumulated.

Label expressions

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 tentative label, is used to gather the information that normal evaluation needs to disambiguate the label. Label expressions specified by the date-as-label and short-label commands are not evaluated tentatively. Normal and tentative evaluation are the same for all types of expression other than @, *, and % expressions. The description below applies to normal evaluation, except where otherwise specified.

field [n]

is the nth part of field. If n is omitted, it defaults to 1.

'string'

The characters in string literally.

@

All authors joined as specified by the join-authors command. The whole of each author's name is used. However, if the references are sorted by author (that is, the sort specification starts with “A+”), then authors' surnames 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. Given any two referenced works with n authors, the use of only the surname for the nth author of a reference is regarded as ambiguous if the other reference shares the first n-1 authors, the nth authors of each reference are not identical, but the nth authors' surnames 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 et-al command; this command may also specify additional requirements that must be met before an initial subsequence can be used. @ tentatively evaluates to a canonical representation of the authors, such that authors that compare equally for sorting purposes have the same representation.

%n

%a

%A

%i

%I

The serial number of the reference formatted according to the character following the %. 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.

expr*

If there is another reference with the same tentative label as this reference, then expr, otherwise an empty string. It tentatively evaluates to an empty string.

expr+n

expr-n

The first (+) or last (-) n upper or lower case letters or digits of expr. roff special characters (such as \('a) count as a single letter. Accent strings are retained but do not count toward the total.

expr.l

expr converted to lowercase.

expr.u

expr converted to uppercase.

expr.c

expr converted to caps and small caps.

expr.r

expr reversed so that the surname is first.

expr.a

expr with first names abbreviated. Fields specified in the abbreviate command are abbreviated before any labels are evaluated. Thus .a is useful only when you want a field to be abbreviated in a label but not in a reference.

expr.y

The year part of expr.

expr.+y

The part of expr before the year, or the whole of expr if it does not contain a year.

expr.-y

The part of expr after the year, or an empty string if expr does not contain a year.

expr.n

The surname part of expr.

expr1~expr2

expr1 except that if the last character of expr1 is - then it will be replaced by expr2.

expr1 expr2

The catenation of expr1 and expr2.

expr1|expr2

If expr1 is non-empty then expr1 otherwise expr2.

expr1&expr2

If expr1 is non-empty then expr2 otherwise an empty string.

expr1?expr2:expr3

If expr1 is non-empty then expr2 otherwise expr3.

<expr>

The label is in two parts, which are separated by 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 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. It is permissible for the first part to be empty; this may be desirable for expressions used in the short-label command.

(expr)

The same as expr. Used for grouping.

The above expressions are listed in order of precedence (highest first); & and | have the same precedence.

Macro interface

Each reference starts with a call to the macro ]-. The string [F will be defined to be the label for this reference, unless the no-label-in-reference command has been given. There then follows a series of string definitions, one for each field: string [X corresponds to field X. The register [P is set to 1 if the P field contains a range of pages. The [T, [A and [O registers are set to 1 according as the T, A and O fields end with any of .?! (an end-of-sentence character). The [E register will be set to 1 if the [E string contains more than one name. The reference is followed by a call to the ][ macro. The first argument to this macro gives a number representing the type of the reference. If a reference contains a J field, it will be classified as type 1, otherwise if it contains a B field, it will be type 3, otherwise if it contains a G or R field it will be type 4, otherwise if it contains an I field it will be type 2, otherwise it will be type 0. The second argument is a symbolic name for the type: other, journal-article, book, article-in-book, or tech-report. Groups of references that have been accumulated or are produced by the bibliography command are preceded by a call to the ]< macro and followed by a call to the ]> macro.