The bibliographic database is a text file consisting of records separated by one
  or more blank lines. Within each record fields start with a % at the
  beginning of a line. Each field has a one character name that immediately
  follows the %. 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:
  - A
- The name of an author. If the name contains a title such as Jr. at
      the end, it should be separated from the last name by a comma. There can
      be multiple occurrences of the A field. The order is significant.
      It is a good idea always to supply an A field or a Q
    field.
- B
- For an article that is part of a book, the title of the book.
- C
- The place (city) of publication.
- 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 D field; if the date is unknown, a value such as
      in press or unknown can be used.
- 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 A fields and , (ed) or
      , (eds) should be appended to the last author.
- G
- US Government ordering number.
- I
- The publisher (issuer).
- J
- For an article in a journal, the name of the journal.
- K
- Keywords to be used for searching.
- L
- Label.
- N
- Journal issue number.
- O
- Other information. This is usually printed at the end of the
    reference.
- P
- Page number. A range of pages can be specified as
      m-n.
- Q
- The name of the author, if the author is not a person. This will only be
      used if there are no A fields. There can only be one Q
      field.
- R
- Technical report number.
- S
- Series name.
- T
- Title. For an article in a book or journal, this should be the title of
      the article.
- V
- Volume number of the journal or book.
- X
- Annotation.
For all fields except A and E, if there is more than
    one occurrence of a particular field in a record, only the last such field
    will be used.
If accent strings are used, they should follow the character to be
    accented. This means that the AM macro must be used with the
    -ms macros. Accent strings should not be quoted: use one \
    rather than two.
The format of a citation is
.[opening-text
flags keywords
fields
.]closing-text
The opening-text, closing-text and flags
    components are optional. Only one of the keywords and fields
    components need be specified.
The keywords component says to search the bibliographic
    databases for a reference that contains all the words in keywords. It
    is an error if more than one reference if found.
The fields components specifies additional fields to
    replace or supplement those specified in the reference. When references are
    being accumulated and the 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.
The opening-text and closing-text component
    specifies strings to be used to bracket the label instead of the strings
    specified in the bracket-label command. If either of these components
    is non-empty, the strings specified in the bracket-label command will
    not be used; this behaviour can be altered using the [ and ]
    flags. Note that leading and trailing spaces are significant for these
    components.
The 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:
  - #
- This says to use the label specified by the short-label command,
      instead of that specified by the 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 # is supposed to be
      suggestive of a numeric type of label.
- [
- Precede opening-text with the first string specified in the
      bracket-label command.
- ]
- Follow closing-text with the second string specified in the
      bracket-label command.
One advantages of using the [ and ] flags rather
    than including the brackets in opening-text and closing-text
    is that you can change the style of bracket used in the document just by
    changing the bracket-label command. Another advantage is that sorting
    and merging of citations will not necessarily be inhibited if the flags are
    used.
If a label is to be inserted into the text, it will be attached to
    the line preceding the .[ line. If there is no such line, then an
    extra line will be inserted before the .[ line and a warning will be
    given.
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 <> label
    expression, and of the sort-adjacent-labels and
    abbreviate-label-ranges command. A label will not be merged if its
    citation has a non-empty opening-text or closing-text.
    However, the labels for a citation using the ] flag and without any
    closing-text immediately followed by a citation using the [
    flag and without any opening-text may be sorted and merged even
    though the first citation's opening-text or the second citation's
    closing-text is non-empty. (If you wish to prevent this just make the
    first citation's closing-text \&.)
Commands are contained between lines starting with .R1 and .R2.
  Recognition of these lines can be prevented by the -R option. When a
  .R1 line is recognized any accumulated references are flushed out.
  Neither .R1 nor .R2 lines, nor anything between them is output.
Commands are separated by newlines or ;s. #
    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 " extends
    to the next " that is not followed by another ". If
    there is no such " the word extends to the end of the line.
    Pairs of " in a word beginning with " collapse to a
    single ". Neither # nor ; are recognized inside
    "s. A line can be continued by ending it with \; this
    works everywhere except after a #.
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; filename 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 last
      name by string2, and from anything else (such as a 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
  
  - .[
    
 $LIST$
 .]
is encountered, after all input files hve been processed, and
    whenever .R1 line is recognized.
 
  - annotate* field string
- field is an annotation; print it at the end of the reference as a
      paragraph preceded by the line
  
  - .string
If macro is omitted it will default to AP; if
    field is also omitted it will default to X. Only one field can
    be an annotation.
 
  - articles string...
- string... are definite or indefinite articles, and should be
      ignored at the beginning of T fields when sorting. Initially,
      the, a and an are recognized as articles.
- bibliography filename...
- Write out all the references contained in the bibliographic databases
      filename... This command should come last in a
      .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 behaviour is
  
  - 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 filename...
- Search the bibliographic databases filename... For each
      filename if an index filename.i created by
      indxbib(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 the 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 no-label-in-reference command. For
    example,
  
  - date-as-label D.+yD.y%a*D.-y
would attach a disambiguating letter to the year part of the
    D field in the reference.
 
  - default-database*
- The default database should be searched. This is the default behaviour, so
      the negative version of this command is more useful. refer
      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
- Control use of et al in the evaluation of @ expressions in
      label expressions. If the number of authors needed to make the author
      sequence unambiguous is u 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 behaviour is
  - include filename
- Include filename and interpret the contents as commands.
- join-authors string1 string2 string3
- This says how authors should be joined together. 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
    "
will restore the default method for joining authors.
 
  - label-in-reference*
- When outputting the reference, define the string [F to be the
      reference's label. This is the default behaviour; 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 behaviour; 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. It is
      usually a good idea to give this command unless you are using
      superscripted numbers as labels.
- reverse* string
- Reverse the fields whose names are in 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.
- 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. (The Label
      expressions subsection 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 will have no effect
      unless references are being accumulated.