### URLs in BibTeX bibliographies

There is no citation type for URLs, per se, in the standard BibTeX styles, though Oren Patashnik (the author of BibTeX) is believed to beconsidering developing one such for use with the long-awaited BibTeX version 1.0.

The actual information that need be available in a citation of an URL is discussed at some length in the publicly available on-line extracts of ISO 690-2; the techniques below do not satisfy all the requirements of ISO 690-2, but they offer a solution that is at least available to users of today's tools.

Until the new version of BibTeX arrives, the simplest technique is to use the `howpublished` field of the standard styles' `@misc` function. Of course, the strictures about typesetting URLs still apply, so the entry will look like:

      @misc{...,
        ...,
        howpublished = "\url{http://...}"
      }

A possible alternative approach is to use BibTeX styles other than the standard ones, that already have URL entry types. Pre-eminent are the natbib styles (plainnat, unsrtnat and abbrevnat). These styles are extensions of the standard styles, principally for use with natbib itself, but they've acquired URLs and other "modern" entries along the way. The same author's custom-bib is also capable of generating styles that honour URL entries.

Another candidate is the harvard package (if its citation styles are otherwise satisfactory for you). Harvard bibliography styles all include a "`url`" field in their specification; however, the typesetting offered is somewhat feeble (though it does recognise and use LaTeX2HTML macros if they are available, to create hyperlinks).

You can also acquire new BibTeX styles by use of Norman Gray's urlbst system, which is based on a perl script that edits an existing BibTeX style file to produce a new style. The new style thus generated has a `webpage` entry type, and also offers support for `url` and `lastchecked` fields in the other entry types. The perl script comes with a set of converted versions of the standard bibliography styles. Documentation is distributed as LaTeX source.

Another possibility is that some conventionally-published paper, technical report (or even book) is also available on the Web. In such cases, a useful technique is something like:

      @techreport{...,
        ...,
        note = "Also available as \url{http://...}"
      }

There is good reason to use the url or hyperref packages in this context, since (by default) the `\url` command ignores spaces in its argument. BibTeX has a habit of splitting lines it considers excessively long, and if there are no space characters for it to use as 'natural' breakpoints, BibTeX will insert a comment ('`%`') character ... which is an acceptable character in an URL, so that `\url` will typeset it. If you're using url, the way around the problem is to insert odd spaces inside the URL itself in the `.bib` file, to enable BibTeX to make reasonable decisions about breaking the line. Note that the version of `\url` that comes with recent versions of the hyperref package doesn't suffer from the '`%`-end of line' problem: hyperref spots the problem, and suppresses the unwanted characters.

`custom-bib bundle`
  macros/latex/contrib/custom-bib (zip, browse)
`harvard.sty`
  macros/latex/contrib/harvard (zip, browse)
`hyperref.sty`
  macros/latex/contrib/hyperref (zip, browse)
`natbib styles`
  macros/latex/contrib/natbib (zip, browse)
`url.sty`
  macros/latex/contrib/misc/url.sty
`urlbst`
  biblio/bibtex/contrib/urlbst (zip, browse)

This question on the Web: http://www.tex.ac.uk/cgi-bin/texfaq2html?label=citeURL