diff --git a/latex/acl_natbib.bst b/latex/acl_natbib.bst
index 7fa70cc..cad5a5e 100644
--- a/latex/acl_natbib.bst
+++ b/latex/acl_natbib.bst
@@ -1,3 +1,16 @@
+%%% Modification of BibTeX style file acl_natbib_nourl.bst
+%%% ... by urlbst, version 0.9.1 (marked with "% urlbst")
+%%% See <https://purl.org/nxg/dist/urlbst> and repository <https://heptapod.host/nxg/urlbst>
+%%% Modifications Copyright 2002–23, Norman Gray,
+%%% and distributed under the terms of the LPPL; see README for discussion.
+%%%
+%%% Added webpage entry type, and url and lastchecked fields.
+%%% Added eprint support.
+%%% Added DOI support.
+%%% Added PUBMED support.
+%%% Added hyperref support.
+%%% Original headers follow...
+
 %%
 %% This is file `acl_natbib_basic.bst',
 %% generated with the docstrip utility.
@@ -78,18 +91,74 @@ ENTRY
     type
     volume
     year
+    doi % urlbst
+    pubmed % urlbst
+    url % urlbst
+    lastchecked % urlbst
   }
   {}
   { label extra.label sort.label short.list }
 INTEGERS { output.state before.all mid.sentence after.sentence after.block }
+% urlbst...
+% urlbst constants and state variables
+STRINGS { urlintro
+  eprinturl eprintprefix doiprefix doiurl pubmedprefix pubmedurl
+  citedstring onlinestring linktextstring
+  openinlinelink closeinlinelink }
+INTEGERS { hrefform doiform inlinelinks makeinlinelink
+  addeprints adddoi addpubmed }
+FUNCTION {init.urlbst.variables}
+{
+  % The following constants may be adjusted by hand, if desired
+
+  % The first set allow you to enable or disable certain functionality.
+  #1 'addeprints :=	% 0=no eprints; 1=include eprints
+  #2 'hrefform :=	% 0=no crossrefs; 1=hypertex hrefs; 2=hyperref hrefs
+  #1 'inlinelinks :=	% 0=URLs explicit; 1=URLs attached to titles
+  #1 'adddoi :=	% 0=no DOI resolver; 1=include it
+  #1 'addpubmed :=	% 0=no PUBMED resolver; 1=include it
+  #0 'doiform :=	% 0=with href; 1=with \doi{}
+
+  % String constants, which you _might_ want to tweak.
+  "online" 'onlinestring :=	% label that a resource is online
+  "[link]" 'linktextstring :=	% anonymous link text
+  "http://www.ncbi.nlm.nih.gov/pubmed/" 'pubmedurl :=	% prefix to make URL from PUBMED
+  "https://doi.org/" 'doiurl :=	% prefix to make URL from DOI
+  "doi:" 'doiprefix :=	% printed text to introduce DOI
+  "https://arxiv.org/abs/" 'eprinturl :=	% prefix to make URL from eprint ref
+  "cited " 'citedstring :=	% label in "lastchecked" remark
+  "arXiv:" 'eprintprefix :=	% text prefix printed before eprint ref
+  "PMID:" 'pubmedprefix :=	% text prefix printed before PUBMED ref
+  "URL: " 'urlintro :=	% text prefix before URL
+
+  % The following are internal state variables, not configuration constants,
+  % so they shouldn't be fiddled with.
+  #0 'makeinlinelink :=     % state variable managed by possibly.setup.inlinelink
+  "" 'openinlinelink :=     % ditto
+  "" 'closeinlinelink :=    % ditto
+}
+INTEGERS {
+  bracket.state
+  outside.brackets
+  open.brackets
+  within.brackets
+  close.brackets
+}
+% ...urlbst to here
 FUNCTION {init.state.consts}
-{ #0 'before.all :=
+{ #0 'outside.brackets := % urlbst...
+  #1 'open.brackets :=
+  #2 'within.brackets :=
+  #3 'close.brackets := % ...urlbst to here
+
+  #0 'before.all :=
   #1 'mid.sentence :=
   #2 'after.sentence :=
   #3 'after.block :=
 }
 STRINGS { s t}
-FUNCTION {output.nonnull}
+% urlbst
+FUNCTION {output.nonnull.original}
 { 's :=
   output.state mid.sentence =
     { ", " * write$ }
@@ -109,6 +178,125 @@ FUNCTION {output.nonnull}
   if$
   s
 }
+
+% urlbst...
+% Minimal DOI parsing.
+% Given a DOI on the stack, check whether it starts with 'doiurl' or not.
+% In either case, leave on the stack first a DOI with, and then a DOI without, the URL prefix.
+FUNCTION {parse.doi}
+{
+  #1 doiurl text.length$ substring$
+  doiurl =
+    { doi
+      doi doiurl text.length$ #1 + #999 substring$ }
+    { doiurl doi *
+      doi }
+  if$
+}
+% The following three functions are for handling inlinelink.  They wrap
+% a block of text which is potentially output with write$ by multiple
+% other functions, so we don't know the content a priori.
+% They communicate between each other using the variables makeinlinelink
+% (which is true if a link should be made), and closeinlinelink (which holds
+% the string which should close any current link.  They can be called
+% at any time, but start.inlinelink will be a no-op unless something has
+% previously set makeinlinelink true, and the two ...end.inlinelink functions
+% will only do their stuff if start.inlinelink has previously set
+% closeinlinelink to be non-empty.
+% (thanks to 'ijvm' for suggested code here)
+FUNCTION {uand}
+{ 'skip$ { pop$ #0 } if$ } % 'and' (which isn't defined at this point in the file)
+FUNCTION {possibly.setup.inlinelink}
+{ makeinlinelink hrefform #0 > uand
+    { doi empty$ adddoi uand
+        { pubmed empty$ addpubmed uand
+            { eprint empty$ addeprints uand
+                { url empty$
+                    { "" }
+                    { url }
+                  if$ }
+                { eprinturl eprint * }
+              if$ }
+            { pubmedurl pubmed * }
+          if$ }
+%        { doiurl doi * }
+        { doi empty$
+            { "XXX" }
+            { doi parse.doi pop$ }
+          if$
+        }
+      if$
+      % an appropriately-formatted URL is now on the stack
+      hrefform #1 = % hypertex
+        { "\special {html:<a href=" quote$ * swap$ * quote$ * "> }{" * 'openinlinelink :=
+          "\special {html:</a>}" 'closeinlinelink := }
+        { "\href {" swap$ * "} {" * 'openinlinelink := % hrefform=#2 -- hyperref
+          % the space between "} {" matters: a URL of just the right length can cause "\% newline em"
+          "}" 'closeinlinelink := }
+      if$
+      #0 'makeinlinelink :=
+      }
+    'skip$
+  if$ % makeinlinelink
+}
+FUNCTION {add.inlinelink}
+{ openinlinelink empty$
+    'skip$
+    { openinlinelink swap$ * closeinlinelink *
+      "" 'openinlinelink :=
+      }
+  if$
+}
+FUNCTION {output.nonnull}
+{ % Save the thing we've been asked to output
+  's :=
+  % If the bracket-state is close.brackets, then add a close-bracket to
+  % what is currently at the top of the stack, and set bracket.state
+  % to outside.brackets
+  bracket.state close.brackets =
+    { "]" *
+      outside.brackets 'bracket.state :=
+    }
+    'skip$
+  if$
+  bracket.state outside.brackets =
+    { % We're outside all brackets -- this is the normal situation.
+      % Write out what's currently at the top of the stack, using the
+      % original output.nonnull function.
+      s
+      add.inlinelink
+      output.nonnull.original % invoke the original output.nonnull
+    }
+    { % Still in brackets.  Add open-bracket or (continuation) comma, add the
+      % new text (in s) to the top of the stack, and move to the close-brackets
+      % state, ready for next time (unless inbrackets resets it).  If we come
+      % into this branch, then output.state is carefully undisturbed.
+      bracket.state open.brackets =
+        { " [" * }
+        { ", " * } % bracket.state will be within.brackets
+      if$
+      s *
+      close.brackets 'bracket.state :=
+    }
+  if$
+}
+
+% Call this function just before adding something which should be presented in
+% brackets.  bracket.state is handled specially within output.nonnull.
+FUNCTION {inbrackets}
+{ bracket.state close.brackets =
+    { within.brackets 'bracket.state := } % reset the state: not open nor closed
+    { open.brackets 'bracket.state := }
+  if$
+}
+
+FUNCTION {format.lastchecked}
+{ lastchecked empty$
+    { "" }
+    { inbrackets citedstring lastchecked * }
+  if$
+}
+% ...urlbst to here
 FUNCTION {output}
 { duplicate$ empty$
     'pop$
@@ -122,7 +310,7 @@ FUNCTION {output.check}
     'output.nonnull
   if$
 }
-FUNCTION {fin.entry}
+FUNCTION {fin.entry.original} % urlbst (renamed from fin.entry, so it can be wrapped below)
 { add.period$
   write$
   newline$
@@ -558,7 +746,7 @@ FUNCTION {make.full.names}
   if$
 }
 
-FUNCTION {output.bibitem}
+FUNCTION {output.bibitem.original} % urlbst (renamed from output.bibitem, so it can be wrapped below)
 { newline$
   "\bibitem[{" write$
   label write$
@@ -935,12 +1123,203 @@ FUNCTION {output.eprint} % this is only used with the @misc record type (common
   if$
 }
 
+% urlbst...
+% Functions for making hypertext links.
+% In all cases, the stack has (link-text href-url)
+%
+% make 'null' specials
+FUNCTION {make.href.null}
+{
+  pop$
+}
+% make hypertex specials
+FUNCTION {make.href.hypertex}
+{
+  "\special {html:<a href=" quote$ *
+  swap$ * quote$ * "> }" * swap$ *
+  "\special {html:</a>}" *
+}
+% make hyperref specials
+FUNCTION {make.href.hyperref}
+{
+  "\href {" swap$ * "} {\path{" * swap$ * "}}" *
+}
+FUNCTION {make.href}
+{ hrefform #2 =
+    'make.href.hyperref      % hrefform = 2
+    { hrefform #1 =
+        'make.href.hypertex  % hrefform = 1
+        'make.href.null      % hrefform = 0 (or anything else)
+      if$
+    }
+  if$
+}
+
+% If inlinelinks is true, then format.url should be a no-op, since it's
+% (a) redundant, and (b) could end up as a link-within-a-link.
+FUNCTION {format.url}
+{ inlinelinks #1 = url empty$ or
+   { "" }
+   { hrefform #1 =
+       { % special case -- add HyperTeX specials
+         urlintro "\url{" url * "}" * url make.href.hypertex * }
+       { urlintro "\url{" * url * "}" * }
+     if$
+   }
+  if$
+}
+FUNCTION {format.eprint}
+{ eprint empty$
+    { "" }
+    { eprintprefix eprint * eprinturl eprint * make.href }
+  if$
+}
+
+FUNCTION {format.doi}
+{ doi empty$
+    { "" }
+    { doi parse.doi % leaves "https://doi.org/DOI" DOI on the stack
+      's := 't :=
+      doiform #1 =
+        { "\doi{" s * "}" * }
+        { doiprefix s * t make.href }
+      if$
+    }
+  if$
+}
+
+FUNCTION {format.pubmed}
+{ pubmed empty$
+    { "" }
+    { pubmedprefix pubmed * pubmedurl pubmed * make.href }
+  if$
+}
+
+% Output a URL.  We can't use the more normal idiom (something like
+% `format.url output'), because the `inbrackets' within
+% format.lastchecked applies to everything between calls to `output',
+% so that `format.url format.lastchecked * output' ends up with both
+% the URL and the lastchecked in brackets.
+FUNCTION {output.url}
+{ url empty$
+    'skip$
+    { new.block
+      format.url output
+      format.lastchecked output
+    }
+  if$
+}
+
+FUNCTION {output.web.refs}
+{
+  new.block
+  inlinelinks
+    'skip$ % links were inline -- don't repeat them
+    { % If the generated DOI will be the same as the URL,
+      % then don't print the URL (thanks to Joseph Wright
+      % for (the original version of) this code,
+      % at http://tex.stackexchange.com/questions/5660)
+      adddoi
+          doi empty$ { "X" } { doi parse.doi pop$ } if$ % DOI URL to be generated
+          url empty$ { "Y" } { url } if$          % the URL, or "Y" if empty
+          =                                       % are the strings equal?
+          and
+        'skip$
+        { output.url }
+      if$
+      addeprints eprint empty$ not and
+        { format.eprint output.nonnull }
+        'skip$
+      if$
+      adddoi doi empty$ not and
+        { format.doi output.nonnull }
+        'skip$
+      if$
+      addpubmed pubmed empty$ not and
+        { format.pubmed output.nonnull }
+        'skip$
+      if$
+    }
+  if$
+}
+
+% Wrapper for output.bibitem.original.
+% If the URL field is not empty, set makeinlinelink to be true,
+% so that an inline link will be started at the next opportunity
+FUNCTION {output.bibitem}
+{ outside.brackets 'bracket.state :=
+  output.bibitem.original
+  inlinelinks url empty$ not doi empty$ not or pubmed empty$ not or eprint empty$ not or and
+    { #1 'makeinlinelink := }
+    { #0 'makeinlinelink := }
+  if$
+}
+
+% Wrapper for fin.entry.original
+FUNCTION {fin.entry}
+{ output.web.refs  % urlbst
+  makeinlinelink       % ooops, it appears we didn't have a title for inlinelink
+    { possibly.setup.inlinelink % add some artificial link text here, as a fallback
+      linktextstring output.nonnull }
+    'skip$
+  if$
+  bracket.state close.brackets = % urlbst
+    { "]" * }
+    'skip$
+  if$
+  fin.entry.original
+}
+
+% Webpage entry type.
+% Title and url fields required;
+% author, note, year, month, and lastchecked fields optional
+% See references
+%   ISO 690-2 http://www.nlc-bnc.ca/iso/tc46sc9/standard/690-2e.htm
+%   http://www.classroom.net/classroom/CitingNetResources.html
+%   http://neal.ctstateu.edu/history/cite.html
+%   http://www.cas.usf.edu/english/walker/mla.html
+% for citation formats for web pages.
+FUNCTION {webpage}
+{ output.bibitem
+  author empty$
+    { editor empty$
+        'skip$  % author and editor both optional
+        { format.editors output.nonnull }
+      if$
+    }
+    { editor empty$
+        { format.authors output.nonnull }
+        { "can't use both author and editor fields in " cite$ * warning$ }
+      if$
+    }
+  if$
+  new.block
+  title empty$ 'skip$ 'possibly.setup.inlinelink if$
+  format.title "title" output.check
+  inbrackets onlinestring output
+  new.block
+  year empty$
+    'skip$
+    { format.date "year" output.check }
+  if$
+  % We don't need to output the URL details ('lastchecked' and 'url'),
+  % because fin.entry does that for us, using output.web.refs.  The only
+  % reason we would want to put them here is if we were to decide that
+  % they should go in front of the rather miscellaneous information in 'note'.
+  new.block
+  note output
+  fin.entry
+}
+% ...urlbst to here
+
+
 FUNCTION {article}
 { output.bibitem
   format.authors "author" output.check
   author format.key output
   format.date "year" output.check
   date.block
+  title empty$ 'skip$ 'possibly.setup.inlinelink if$ % urlbst
   format.title "title" output.check
   new.block
   crossref missing$
@@ -949,7 +1328,7 @@ FUNCTION {article}
       "journal" bibinfo.check
       emphasize
       "journal" output.check
-      format.vol.num.pages output
+      possibly.setup.inlinelink format.vol.num.pages output% urlbst
     }
     { format.article.crossref output.nonnull
       format.pages output
@@ -974,6 +1353,7 @@ FUNCTION {book}
   if$
   format.date "year" output.check
   date.block
+  title empty$ 'skip$ 'possibly.setup.inlinelink if$ % urlbst
   format.btitle "title" output.check
   format.edition output
   crossref missing$
@@ -998,6 +1378,7 @@ FUNCTION {booklet}
   author format.key output
   format.date "year" output.check
   date.block
+  title empty$ 'skip$ 'possibly.setup.inlinelink if$ % urlbst
   format.title "title" output.check
   new.block
   howpublished "howpublished" bibinfo.check output
@@ -1022,6 +1403,7 @@ FUNCTION {inbook}
   if$
   format.date "year" output.check
   date.block
+  title empty$ 'skip$ 'possibly.setup.inlinelink if$ % urlbst
   format.btitle "title" output.check
   crossref missing$
     {
@@ -1050,6 +1432,7 @@ FUNCTION {incollection}
   author format.key output
   format.date "year" output.check
   date.block
+  title empty$ 'skip$ 'possibly.setup.inlinelink if$ % urlbst
   format.title "title" output.check
   new.block
   crossref missing$
@@ -1075,6 +1458,7 @@ FUNCTION {inproceedings}
   author format.key output
   format.date "year" output.check
   date.block
+  title empty$ 'skip$ 'possibly.setup.inlinelink if$ % urlbst
   format.title "title" output.check
   new.block
   crossref missing$
@@ -1102,6 +1486,7 @@ FUNCTION {manual}
   author format.key output
   format.date "year" output.check
   date.block
+  title empty$ 'skip$ 'possibly.setup.inlinelink if$ % urlbst
   format.btitle "title" output.check
   format.edition output
   organization address new.block.checkb
@@ -1118,6 +1503,7 @@ FUNCTION {mastersthesis}
   author format.key output
   format.date "year" output.check
   date.block
+  title empty$ 'skip$ 'possibly.setup.inlinelink if$ % urlbst
   format.title
   "title" output.check
   new.block
@@ -1136,6 +1522,7 @@ FUNCTION {misc}
   author format.key output
   format.date "year" output.check
   date.block
+  title empty$ 'skip$ 'possibly.setup.inlinelink if$ % urlbst
   format.title output
   new.block
   howpublished "howpublished" bibinfo.check output
@@ -1151,6 +1538,7 @@ FUNCTION {phdthesis}
   author format.key output
   format.date "year" output.check
   date.block
+  title empty$ 'skip$ 'possibly.setup.inlinelink if$ % urlbst
   format.btitle
   "title" output.check
   new.block
@@ -1167,6 +1555,7 @@ FUNCTION {presentation}
   format.authors output
   author format.key output
   new.block
+  title empty$ 'skip$ 'possibly.setup.inlinelink if$ % urlbst
   format.title output
   new.block
   format.organization.address "organization and address" output.check
@@ -1187,6 +1576,7 @@ FUNCTION {proceedings}
   editor format.key output
   format.date "year" output.check
   date.block
+  title empty$ 'skip$ 'possibly.setup.inlinelink if$ % urlbst
   format.btitle "title" output.check
   format.bvolume output
   format.number.series output
@@ -1209,6 +1599,7 @@ FUNCTION {techreport}
   author format.key output
   format.date "year" output.check
   date.block
+  title empty$ 'skip$ 'possibly.setup.inlinelink if$ % urlbst
   format.title
   "title" output.check
   new.block
@@ -1226,6 +1617,7 @@ FUNCTION {unpublished}
   author format.key output
   format.date "year" output.check
   date.block
+  title empty$ 'skip$ 'possibly.setup.inlinelink if$ % urlbst
   format.title "title" output.check
   new.block
   format.note "note" output.check
@@ -1523,6 +1915,7 @@ FUNCTION {begin.bib}
   write$ newline$
 }
 EXECUTE {begin.bib}
+EXECUTE {init.urlbst.variables} % urlbst
 EXECUTE {init.state.consts}
 ITERATE {call.type$}
 FUNCTION {end.bib}