citation information to be specified in Iris documentation.
BibTeX entry example

@Manual{Iris,
author = {{Met Office}},
title = {Iris: A Python library for analysing and visualising meteorological and oceanographic data sets},
year = {2010 - 2013},
address = {Exeter, Devon },
url = {http://scitools.org.uk/}
}

Using use Software Sustainability Institute conventions.

If software downloaded:
ProductName. Version. ReleaseDate. Publisher. Location. DOIorURL. DownloadDate.

for example:
Iris. V1.2. 28-Feb-2013. Met Office. UK. https://github.com/SciTools/iris/archive/v1.2.0.tar.gz 01-03-2013

If software checked out:
ProductName. Publisher. URL. CheckoutDate. RepositorySpecificCheckoutInformation.

for example:
Iris. Met Office. [email protected]:SciTools/iris.git 06-03-2013

Reference used
Jackson, M. 2012. 'How to cite and describe software'. [online] Available at < http://software.ac.uk/so-exactly-what-software-did-you-use> Accessed 06/03/2013