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I would like to use the natbib command \citet with a custom .bst file. But the pdf file contains "(authors?)" instead (see Why do I get (author?) when I use \citet with natbib?).

How can I fix this without using predefined natbib style (like plainnat)?

I remarked that the aux file contains a bibcite command that looks like this : \bibcite{foo2008}{{Foo~2008}{}{{}}{{}}}. If I manually edit this command I can easily obtain a similar result as when using predefined natbib style.

What is responsible for generating the bibcite command? How to include more information? Is it a function from the bst style file?

I would like to edit my bst file only. Here are my files:

%
% Style de bibliographie pour the`se - d'apres alpha.bst
%
% Matthieu Herrb (matthieu@laas.fr) - Juillet 89, Octobre 90
%
%        Les references seront designees tant dans le texte que dans
% la liste recapitulative (ordonnee suivant l'ordre alphabetique du nom
% du premier auteur), par le nom du premier auteur suivi des deux
% derniers chiffres de l'annee de publication, le tout entre crochets.
% Si deux references du meme auteur se rapportent a la meme annee, elles
% seront differenciees par des lettres minuscules (a, b, etc.)
%
% version 0.99a for BibTeX versions 0.99a or later, LaTeX version 2.09.
% Copyright (C) 1985, all rights reserved.
% Copying of this file is authorized only if either
% (1) you make absolutely no changes to your copy, including name, or
% (2) if you do make changes, you name it something other than
% btxbst.doc, plain.bst, unsrt.bst, alpha.bst, and abbrv.bst.
% This restriction helps ensure that all standard styles are identical.

ENTRY { address author booktitle chapter edition editor howpublished institution journal key month note number organization pages publisher school series title type volume year } {} { label extra.label sort.label }

INTEGERS { output.state before.all mid.sentence after.sentence after.block }

FUNCTION {init.state.consts} { #0 'before.all := #1 'mid.sentence := #2 'after.sentence := #3 'after.block := }

STRINGS { s t }

FUNCTION {output.nonnull} { 's := output.state mid.sentence = { ", " * write$ } { output.state after.block = { add.period$ write$ newline$ "\newblock " write$ } { output.state before.all = 'write$ { add.period$ " " * write$ } if$ } if$ mid.sentence 'output.state := } if$ s }

FUNCTION {output} { duplicate$ empty$ 'pop$ 'output.nonnull if$ }

FUNCTION {output.check} { 't := duplicate$ empty$ { pop$ "empty " t * " in " * cite$ * warning$ } 'output.nonnull if$ }

FUNCTION {output.bibitem} { newline$ "\bibitem[" write$ label write$ "]{" write$ cite$ write$ "}" write$ newline$ "" before.all 'output.state := }

FUNCTION {fin.entry} { add.period$ write$ newline$ }

FUNCTION {new.block} { output.state before.all = 'skip$ { after.block 'output.state := } if$ }

FUNCTION {new.sentence} { output.state after.block = 'skip$ { output.state before.all = 'skip$ { after.sentence 'output.state := } if$ } if$ }

FUNCTION {not} { { #0 } { #1 } if$ }

FUNCTION {and} { 'skip$ { pop$ #0 } if$ }

FUNCTION {or} { { pop$ #1 } 'skip$ if$ }

FUNCTION {new.block.checka} { empty$ 'skip$ 'new.block if$ }

FUNCTION {new.block.checkb} { empty$ swap$ empty$ and 'skip$ 'new.block if$ }

FUNCTION {new.sentence.checka} { empty$ 'skip$ 'new.sentence if$ }

FUNCTION {new.sentence.checkb} { empty$ swap$ empty$ and 'skip$ 'new.sentence if$ }

FUNCTION {field.or.null} { duplicate$ empty$ { pop$ "" } 'skip$ if$ }

FUNCTION {emphasize} { duplicate$ empty$ { pop$ "" } { "{\em " swap$ * "}" * } if$ }

FUNCTION {scapify} { duplicate$ empty$ { pop$ "" } { "{\sc " swap$ * "}" * } if$ }

FUNCTION {underline} { duplicate$ empty$ { pop$ "" } { "{\ul " swap$ * "}" * } if$ }

INTEGERS { nameptr namesleft numnames }

FUNCTION {format.names} { 's := #1 'nameptr := s num.names$ 'numnames := numnames 'namesleft := { namesleft #0 > } { s nameptr "{ff~}{vv~}{ll}{~jj}" format.name$ 't := nameptr #1 > { namesleft #1 > { ", " * t * } { numnames #2 > { "" * } 'skip$ if$ t "others" = { " et~al." emphasize * } { " \iftoggle{ThesisInEnglish}{and}{et} " * t * } if$ } if$ } 't if$ nameptr #1 + 'nameptr := namesleft #1 - 'namesleft := } while$ }

FUNCTION {format.authors} { author empty$ { "" } { author format.names } if$ }

FUNCTION {format.editors} { editor empty$ { "" } { editor format.names editor num.names$ #1 > { ", \iftoggle{ThesisInEnglish}{editors}{editeurs}" * } { ", \iftoggle{ThesisInEnglish}{editor}{editeur}" * } if$ } if$ }

FUNCTION {format.title} { title empty$ { "" } { title "t" change.case$ } if$ }

FUNCTION {n.dashify} { 't := "" { t empty$ not } { t #1 #1 substring$ "-" = { t #1 #2 substring$ "--" = not { "--" * t #2 global.max$ substring$ 't := } { { t #1 #1 substring$ "-" = } { "-" * t #2 global.max$ substring$ 't := } while$ } if$ } { t #1 #1 substring$ * t #2 global.max$ substring$ 't := } if$ } while$ }

FUNCTION {format.date} { year empty$ { month empty$ { "" } { "there's a month but no year in " cite$ * warning$ month } if$ } { month empty$ 'year { month " " * year * } if$ } if$ }

FUNCTION {format.btitle} { title emphasize }

FUNCTION {format.utitle} { title emphasize }

FUNCTION {tie.or.space.connect} { duplicate$ text.length$ #3 < { "~" } { " " } if$ swap$ * * }

FUNCTION {either.or.check} { empty$ 'pop$ { "can't use both " swap$ * " fields in " * cite$ * warning$ } if$ }

FUNCTION {format.bvolume} { volume empty$ { "" } { "volume" volume tie.or.space.connect series empty$ 'skip$ { " of " * series emphasize * } if$ "volume and number" number either.or.check } if$ }

FUNCTION {format.number.series} { volume empty$ { number empty$ { series field.or.null } { output.state mid.sentence = { "\iftoggle{ThesisInEnglish}{number}{num'ero}" } { "\iftoggle{ThesisInEnglish}{Number}{Nume'ero}" } if$ number tie.or.space.connect series empty$ { "there's a number but no series in " cite$ * warning$ } { " \iftoggle{ThesisInEnglish}{in}{de} " * series * } if$ } if$ } { "" } if$ }

FUNCTION {format.edition} { edition empty$ { "" } { output.state mid.sentence = { edition "l" change.case$ " \iftoggle{ThesisInEnglish}{edition}{'edition}" * } { edition "t" change.case$ " \iftoggle{ThesisInEnglish}{edition}{'edition}" * } if$ } if$ }

INTEGERS { multiresult }

FUNCTION {multi.page.check} { 't := #0 'multiresult := { multiresult not t empty$ not and } { t #1 #1 substring$ duplicate$ "-" = swap$ duplicate$ "," = swap$ "+" = or or { #1 'multiresult := } { t #2 global.max$ substring$ 't := } if$ } while$ multiresult }

FUNCTION {format.pages} { pages empty$ { "" } { pages multi.page.check { "pages" pages n.dashify tie.or.space.connect } { "page" pages tie.or.space.connect } if$ } if$ }

FUNCTION {format.volume} { volume empty$ { "" } { "vol.~" volume * } if$ }

FUNCTION {format.number} { number empty$ { "" } { "no.~" number * } if$ }

FUNCTION {format.chapter.pages} { chapter empty$ 'format.pages { type empty$ { "\iftoggle{ThesisInEnglish}{chapter}{chapitre}" } { type "l" change.case$ } if$ chapter tie.or.space.connect pages empty$ 'skip$ { ", " * format.pages * } if$ } if$ }

FUNCTION {format.in.ed.booktitle} { booktitle empty$ { "" } { editor empty$ { "\iftoggle{ThesisInEnglish}{In}{Dans} " booktitle * } { "\iftoggle{ThesisInEnglish}{In}{Dans} " format.editors * ", " * booktitle * } if$ } if$ }

FUNCTION {empty.misc.check} { author empty$ title empty$ howpublished empty$ month empty$ year empty$ note empty$ and and and and and key empty$ not and { "all relevant fields are empty in " cite$ * warning$ } 'skip$ if$ }

FUNCTION {format.thesis.type} { type empty$ 'skip$ { pop$ type "t" change.case$ } if$ }

FUNCTION {format.tr.number} { type empty$ { "\iftoggle{ThesisInEnglish}{Technical Report}{Rapport technique}" } 'type if$ number empty$ { "t" change.case$ } { number tie.or.space.connect } if$ }

FUNCTION {format.article.crossref} { key empty$ { journal empty$ { "need key or journal for " cite$ * " to crossref " * crossref * warning$ "" } { "In {\em " journal * "/}" * } if$ } { "In " key * } if$ " \cite{" * crossref * "}" * }

FUNCTION {format.crossref.editor} { editor #1 "{vv~}{ll}" format.name$ editor num.names$ duplicate$ #2 > { pop$ " et~al." * } { #2 < 'skip$ { editor #2 "{ff }{vv }{ll}{ jj}" format.name$ "others" = { " et~al." * } { " &amp; " * editor #2 "{vv~}{ll}" format.name$ * } if$ } if$ } if$ }

FUNCTION {format.book.crossref} { volume empty$ { "empty volume in " cite$ * "'s crossref of " * crossref * warning$ "In " } { "Volume" volume tie.or.space.connect " of " * } if$ editor empty$ editor field.or.null author field.or.null = or { key empty$ { series empty$ { "need editor, key, or series for " cite$ * " to crossref " * crossref * warning$ "" * } { "{\em " * series * "/}" * } if$ } { key * } if$ } { format.crossref.editor * } if$ " \cite{" * crossref * "}" * }

FUNCTION {format.incoll.inproc.crossref} { editor empty$ editor field.or.null author field.or.null = or { booktitle empty$ { key empty$ { "need editor, key, or booktitle for " cite$ * " to crossref " * crossref * warning$ "" } { "\iftoggle{ThesisInEnglish}{In}{Dans} " key * } if$ } { "\iftoggle{ThesisInEnglish}{In}{Dans} " booktitle * } if$ } { "In " format.crossref.editor * } if$ " \cite{" * crossref * "}" * }

FUNCTION {article} { output.bibitem format.authors "author" output.check new.block format.utitle "title" output.check new.block crossref missing$ { journal "journal" output.check format.volume output format.number output format.pages output format.date "year" output.check } { format.article.crossref output.nonnull format.pages output } if$ new.block note output fin.entry }

FUNCTION {book} { output.bibitem author empty$ { format.editors "author and editor" output.check } { format.authors output.nonnull crossref missing$ { "author and editor" editor either.or.check } 'skip$ if$ } if$ new.block format.title "title" output.check crossref missing$ { format.bvolume output new.block format.number.series output new.sentence publisher "publisher" output.check address output } { new.block format.book.crossref output.nonnull } if$ format.edition output format.date "year" output.check new.block note output fin.entry }

FUNCTION {booklet} { output.bibitem format.authors output new.block format.title "title" output.check howpublished address new.block.checkb howpublished output address output format.date output new.block note output fin.entry }

FUNCTION {inbook} { output.bibitem author empty$ { format.editors "author and editor" output.check } { format.authors output.nonnull crossref missing$ { "author and editor" editor either.or.check } 'skip$ if$ } if$ new.block format.title "title" output.check crossref missing$ { format.bvolume output format.chapter.pages "chapter and pages" output.check new.block format.number.series output new.sentence publisher "publisher" output.check address output } { format.chapter.pages "chapter and pages" output.check new.block format.book.crossref output.nonnull } if$ format.edition output format.date "year" output.check new.block note output fin.entry }

FUNCTION {incollection} { output.bibitem format.authors "author" output.check new.block format.utitle "title" output.check new.block crossref missing$ { format.in.ed.booktitle "booktitle" output.check format.bvolume output format.number.series output format.chapter.pages output new.sentence publisher "publisher" output.check address output format.edition output format.date "year" output.check } { format.incoll.inproc.crossref output.nonnull format.chapter.pages output } if$ new.block note output fin.entry }

FUNCTION {inproceedings} { output.bibitem format.authors "author" output.check new.block format.utitle "title" output.check new.block crossref missing$ { format.in.ed.booktitle "booktitle" output.check format.bvolume output format.number.series output format.pages output address empty$ { organization publisher new.sentence.checkb organization output publisher output format.date "year" output.check } { address output.nonnull format.date "year" output.check new.sentence organization output publisher output } if$ } { format.incoll.inproc.crossref output.nonnull format.pages output } if$ new.block note output fin.entry }

FUNCTION {conference} { inproceedings }

FUNCTION {manual} { output.bibitem author empty$ { organization empty$ 'skip$ { organization output.nonnull address output } if$ } { format.authors output.nonnull } if$ new.block format.utitle "title" output.check author empty$ { organization empty$ { address new.block.checka address output } 'skip$ if$ } { organization address new.block.checkb organization output address output } if$ format.edition output format.date output new.block note output fin.entry }

FUNCTION {mastersthesis} { output.bibitem format.authors "author" output.check new.block format.title "title" output.check new.block "Master's thesis" format.thesis.type output.nonnull school "school" output.check address output format.date "year" output.check new.block note output fin.entry }

FUNCTION {misc} { output.bibitem format.authors output title howpublished new.block.checkb format.utitle output howpublished new.block.checka howpublished output format.date output new.block note output fin.entry empty.misc.check }

FUNCTION {phdthesis} { output.bibitem format.authors "author" output.check new.block format.btitle "title" output.check new.block "PhD thesis" format.thesis.type output.nonnull school "school" output.check address output format.date "year" output.check new.block note output fin.entry }

FUNCTION {proceedings} { output.bibitem editor empty$ { organization output } { format.editors output.nonnull } if$ new.block format.title "title" output.check format.bvolume output format.number.series output address empty$ { editor empty$ { publisher new.sentence.checka } { organization publisher new.sentence.checkb organization output } if$ publisher output format.date "year" output.check } { address output.nonnull format.date "year" output.check new.sentence editor empty$ 'skip$ { organization output } if$ publisher output } if$ new.block note output fin.entry }

FUNCTION {techreport} { output.bibitem format.authors "author" output.check new.block format.utitle "title" output.check new.block format.tr.number output.nonnull institution "institution" output.check address output format.date "year" output.check new.block note output fin.entry }

FUNCTION {unpublished} { output.bibitem format.authors "author" output.check new.block format.title "title" output.check new.block note "note" output.check format.date output fin.entry }

FUNCTION {default.type} { misc }

MACRO {jan} {"\monthname[1]"}

MACRO {feb} {"\monthname[2]"}

MACRO {mar} {"\monthname[3]"}

MACRO {apr} {"\monthname[4]"}

MACRO {may} {"\monthname[5]"}

MACRO {jun} {"\monthname[6]"}

MACRO {jul} {"\monthname[7]"}

MACRO {aug} {"\monthname[8]"}

MACRO {sep} {"\monthname[9]"}

MACRO {oct} {"\monthname[10]"}

MACRO {nov} {"\monthname[11]"}

MACRO {dec} {"\monthname[12]"}

MACRO {acmcs} {"ACM Computing Surveys"}

MACRO {acta} {"Acta Informatica"}

MACRO {cacm} {"Communications of the ACM"}

MACRO {ibmjrd} {"IBM Journal of Research and Development"}

MACRO {ibmsj} {"IBM Systems Journal"}

MACRO {ieeese} {"IEEE Transactions on Software Engineering"}

MACRO {ieeetc} {"IEEE Transactions on Computers"}

MACRO {ieeetcad} {"IEEE Transactions on Computer-Aided Design of Integrated Circuits"}

MACRO {ipl} {"Information Processing Letters"}

MACRO {jacm} {"Journal of the ACM"}

MACRO {jcss} {"Journal of Computer and System Sciences"}

MACRO {scp} {"Science of Computer Programming"}

MACRO {sicomp} {"SIAM Journal on Computing"}

MACRO {tocs} {"ACM Transactions on Computer Systems"}

MACRO {tods} {"ACM Transactions on Database Systems"}

MACRO {tog} {"ACM Transactions on Graphics"}

MACRO {toms} {"ACM Transactions on Mathematical Software"}

MACRO {toois} {"ACM Transactions on Office Information Systems"}

MACRO {toplas} {"ACM Transactions on Programming Languages and Systems"}

MACRO {tcs} {"Theoretical Computer Science"}

READ

FUNCTION {sortify} { purify$ "l" change.case$ }

INTEGERS { len }

FUNCTION {chop.word} { 's := 'len := s #1 len substring$ = { s len #1 + global.max$ substring$ } 's if$ }

INTEGERS { et.al.char.used }

FUNCTION {initialize.et.al.char.used} { #0 'et.al.char.used := }

EXECUTE {initialize.et.al.char.used}

% % Cette function produit le label avec le nom du premier auteur % FUNCTION {format.lab.names} { 's := s #1 "{vv }{ll}" format.name$ }

FUNCTION {author.key.label} { author empty$ { key empty$ { cite$ #1 #3 substring$ } { key #3 } if$ } { author format.lab.names } if$ }

FUNCTION {author.editor.key.label} { author empty$ { editor empty$ { key empty$ { cite$ #1 #3 substring$ } { key } if$ } { editor format.lab.names } if$ } { author format.lab.names } if$ }

FUNCTION {author.key.organization.label} { author empty$ { key empty$ { organization empty$ { cite$ #1 #3 substring$ } { "The " #4 organization chop.word #3 text.prefix$ } if$ } { key } if$ } { author format.lab.names } if$ }

FUNCTION {editor.key.organization.label} { editor empty$ { key empty$ { organization empty$ { cite$ #1 #3 substring$ } { "The " #4 organization chop.word #3 text.prefix$ } if$ } { key } if$ } { editor format.lab.names } if$ }

% % Fonction modifiee pour generer les bons labels FUNCTION {calc.label} { type$ "book" = type$ "inbook" = or 'author.editor.key.label { type$ "proceedings" = 'editor.key.organization.label { type$ "manual" = 'author.key.organization.label 'author.key.label if$ } if$ } if$ duplicate$ "~" * year #-1 #4 substring$ field.or.null purify$ * 'label := year #-1 #4 substring$ field.or.null purify$

sortify 'sort.label := }

FUNCTION {sort.format.names} { 's := #1 'nameptr := "" s num.names$ 'numnames := numnames 'namesleft := { namesleft #0 > } { nameptr #1 > { " " * } 'skip$ if$ s nameptr "{vv{ } }{ll{ }}{ ff{ }}{ jj{ }}" format.name$ 't := nameptr numnames = t "others" = and { "et al" * } { t sortify * } if$ nameptr #1 + 'nameptr := namesleft #1 - 'namesleft := } while$ }

FUNCTION {sort.format.title} { 't := "A " #2 "An " #3 "The " #4 t chop.word chop.word chop.word sortify #1 global.max$ substring$ }

FUNCTION {author.sort} { author empty$ { key empty$ { "to sort, need author or key in " cite$ * warning$ "" } { key sortify } if$ } { author sort.format.names } if$ }

FUNCTION {author.editor.sort} { author empty$ { editor empty$ { key empty$ { "to sort, need author, editor, or key in " cite$ * warning$ "" } { key sortify } if$ } { editor sort.format.names } if$ } { author sort.format.names } if$ }

FUNCTION {author.organization.sort} { author empty$ { organization empty$ { key empty$ { "to sort, need author, organization, or key in " cite$ * warning$ "" } { key sortify } if$ } { "The " #4 organization chop.word sortify } if$ } { author sort.format.names } if$ }

FUNCTION {editor.organization.sort} { editor empty$ { organization empty$ { key empty$ { "to sort, need editor, organization, or key in " cite$ * warning$ "" } { key sortify } if$ } { "The " #4 organization chop.word sortify } if$ } { editor sort.format.names } if$ }

FUNCTION {presort} { calc.label sort.label " "

type$ "book" = type$ "inbook" = or 'author.editor.sort { type$ "proceedings" = 'editor.organization.sort { type$ "manual" = 'author.organization.sort 'author.sort if$ } if$ } if$

" "

year field.or.null sortify

" "

title field.or.null sort.format.title

#1 entry.max$ substring$ 'sort.key$ := }

ITERATE {presort}

SORT

STRINGS { longest.label last.sort.label next.extra }

INTEGERS { longest.label.width last.extra.num }

FUNCTION {initialize.longest.label} { "" 'longest.label := #0 int.to.chr$ 'last.sort.label := "" 'next.extra := #0 'longest.label.width := #0 'last.extra.num := }

FUNCTION {forward.pass} { last.sort.label sort.label = { last.extra.num #1 + 'last.extra.num := last.extra.num int.to.chr$ 'extra.label := } { "a" chr.to.int$ 'last.extra.num := "" 'extra.label := sort.label 'last.sort.label := } if$ }

FUNCTION {reverse.pass} { next.extra "b" = { "a" 'extra.label := } 'skip$ if$ label extra.label * 'label := label width$ longest.label.width > { label 'longest.label := label width$ 'longest.label.width := } 'skip$ if$ extra.label 'next.extra := }

EXECUTE {initialize.longest.label}

ITERATE {forward.pass}

REVERSE {reverse.pass}

FUNCTION {begin.bib} { et.al.char.used { "\newcommand{\etalchar}[1]{$^{#1}$}" write$ newline$ } 'skip$ if$ preamble$ empty$ 'skip$ { preamble$ write$ newline$ } if$ % "\begin{thebibliography}{" longest.label * "}" * write$ newline$ "\begin{thebibliography}{xxxx}" write$ newline$ }

EXECUTE {begin.bib}

EXECUTE {init.state.consts}

ITERATE {call.type$}

FUNCTION {end.bib} { newline$ "\end{thebibliography}" write$ newline$ }

EXECUTE {end.bib}

moewe
  • 175,683
T.L
  • 103

1 Answers1

2

If you want to use a .bst file with natbib's author-year citation module, the .bst file needs to pass on the author and year information in a way readable for natbib. That is done via the optional argument to \bibitem. The comments in natbib.sty explain

 % This package reimplements the LaTeX \cite command to be used for various
 % citation styles, both author-year and numerical. It accepts BibTeX
 % output intended for many other packages, and therefore acts as a
 % general, all-purpose citation-style interface.
 %
 % With standard numerical .bst files, only numerical citations are
 % possible. With an author-year .bst file, both numerical and
 % author-year citations are possible.
 %
 % If author-year citations are selected, \bibitem must have one of the
 %   following forms:
 %   \bibitem[Jones et al.(1990)]{key}...
 %   \bibitem[Jones et al.(1990)Jones, Baker, and Williams]{key}...
 %   \bibitem[Jones et al., 1990]{key}...
 %   \bibitem[\protect\citeauthoryear{Jones, Baker, and Williams}{Jones
 %       et al.}{1990}]{key}...
 %   \bibitem[\protect\citeauthoryear{Jones et al.}{1990}]{key}...
 %   \bibitem[\protect\astroncite{Jones et al.}{1990}]{key}...
 %   \bibitem[\protect\citename{Jones et al., }1990]{key}...
 %   \harvarditem[Jones et al.]{Jones, Baker, and Williams}{1990}{key}...
 %
 % This is either to be made up manually, or to be generated by an
 % appropriate .bst file with BibTeX.

Your .bst file wasn't written with this system in mind (in fact it was written before natbib was even a thing), but it isn't too hard to make it cooperate with natbib.

As you noted, your .bst file generates citation labels of the form

\bibitem[<author>~<year>]

and with two small changes we can make it generate the natbib-compatible

\bibitem[<author>(<year>)]

Just change

FUNCTION {calc.label}
{ type$ "book" =
  type$ "inbook" =
  or
    'author.editor.key.label
    { type$ "proceedings" =
    'editor.key.organization.label
    { type$ "manual" =
        'author.key.organization.label
        'author.key.label
      if$
    }
      if$
    }
  if$
  duplicate$
  "~" *
  year #-1 #4 substring$ field.or.null purify$ *
  'label :=
  year #-1 #4 substring$ field.or.null purify$ 
  *
  sortify 'sort.label :=
}

to

FUNCTION {calc.label}
{ type$ "book" =
  type$ "inbook" =
  or
    'author.editor.key.label
    { type$ "proceedings" =
    'editor.key.organization.label
    { type$ "manual" =
        'author.key.organization.label
        'author.key.label
      if$
    }
      if$
    }
  if$
  duplicate$
  "(" *
  year #-1 #4 substring$ field.or.null purify$ *
  ")" *
  'label :=
  year #-1 #4 substring$ field.or.null purify$ 
  *
  sortify 'sort.label :=
}

The actual diff between these functions is just

--- oldtdotldot.bst 2020-10-09 16:44:49.017918200 +0200
+++ tdotldot.bst    2020-10-09 16:38:01.070090100 +0200
@@ -1038,8 +1038,9 @@
     }
   if$
   duplicate$
-  "~" *
+  "(" *
   year #-1 #4 substring$ field.or.null purify$ *
+  ")" *
   'label :=
   year #-1 #4 substring$ field.or.null purify$ 
   *
moewe
  • 175,683