Encouraging citation of software – introducing CITATION files

Summary: Put a plaintext file named CITATION in the root directory of your code, and put information in it about how to cite your software. Go on, do it now – it’ll only take two minutes!

Software is very important in science – but good software takes time and effort that could be used to do other work instead. I believe that it is important to do this work – but to make it worthwhile, people need to get credit for their work, and in academia that means citations. However, it is often very difficult to find out how to cite a piece of software – sometimes it is hidden away somewhere in the manual or on the web-page, but often it requires sending an email to the author asking them how they want it cited. The effort that this requires means that many people don’t bother to cite the software they use, and thus the authors don’t get the credit that they need. We need to change this, so that software – which underlies a huge amount of important scientific work – gets the recognition it deserves.

As with many things relating to software sustainability in science, the R project does this very well: if you want to find out how to cite the R software itself you simply run the command:

citation()

If you want to find out how to cite a package you simply run:

citation(PROJECTNAME)

For example:

> citation('ggplot2')

To cite ggplot2 in publications, please use:

  H. Wickham. ggplot2: elegant graphics for data analysis. Springer New York,
  2009.

A BibTeX entry for LaTeX users is

  @Book{,
    author = {Hadley Wickham},
    title = {ggplot2: elegant graphics for data analysis},
    publisher = {Springer New York},
    year = {2009},
    isbn = {978-0-387-98140-6},
    url = {http://had.co.nz/ggplot2/book},
  }

In this case the citation was given by the author of the package, in R code, in a file called (surprise, surprise) CITATION inside the package directory. R can even intelligently make up a citation if the author hasn’t provided one. Note also that the function provides a nice handy BibTeX entry for those who use LaTeX – making it even easier to use the citation, and thus reducing the effort involved in citing software properly.

I think the R approach is wonderful, but the exact methods are rather specific to R (it is all based around a citEntry object and the CITATION file contains actual R code). I’d like to suggest a simpler, slightly more flexible approach for use broadly across scientific software:

Create a CITATION file in the root directory of your project and put something in there that tells people how to cite it

In most cases this will probably be some plain-text which gives the citation, and possibly a BibTeX entry for it, but it could be some sort of code (in the language your project uses) which will print out an appropriate citation when run (and, of course, R users should stick to the standard way of writing CITATION files for R packages).

I know this approach isn’t perfect (machine-readability of citations is a problem using this method, but then again machine readability of citations is a big problem generally…) but I think it is a start and hopefully it’ll reduce the effort required to cite software, and thus encourage software citation.

So, go on – go and write a few CITATION files now!