Excursus

Most academic journals in my field publish online as well as print. Increasingly, it is more convenient for me to download an article than to go to the library (especially since my University library has the appalling policy of allowing people to check out journals—which means that there is good chance that what you are looking for won’t be there.) Given the prevalence of articles appearing online, it is useful for your readers to include a link to the relevant url in your bibliography. That way, when reading your pdf, they can click on a link in your bibliography and their default browser automagically launches and takes them to the referenced paper. Too cool.

There are however, problems. Here are two. First, many urls contain “%” characters which will cause LaTeX to choke since it interpret these as a comment character. You could, of course, edit the .bbl file adding escape characters, but a programmatic solution would be better. But any such solution would not be sustainable. Websites move. A url that now works may not work in the future and there is no gurantee that the old url will redirect.

Fortunately, there is a solution to this latter problem—DOI numbers. DOIs or Document Object Identifies provides a framework for the persistent identification of objects online. The DOI system has recently been accepted for standardization by the ISO. Not only are DOIs persistent and so will track the relevant document through changes in urls, but the DOI syntax does not involve any characters that will cause LaTeX to choke. Problem solved. Almost.

Some BibTeX styles, such as natbib supports DOI fields. However, even with loading the hyperref and and url packages, no clickable link is generated. Once you have a DOI number, to make a link, you need to prepend the url of a DOI proxy server, such as http://dx.doi.org/. Place the resulting url:

http://dx.doi.org/DOInumber

in the URL field to yield a stable persistent link to the cited paper.