how to cite software (metis in particular)

I use Metis and ParMetis a lot in my research. How should I cite them in publications? Currently I am using the following:

author = {George Karypis and Vipin Kumar},
title = {{MeTis: Unstructured Graph Partitioning and Sparse Matrix Ordering System, Version 4.0}},
howpublished = {\url{}},
year = {2009},
organization = {University of Minnesota, Minneapolis, MN},

PS: By the way, really nice Drupal site here! Maybe you can add a few more features for the users, such as us posting our own work with [Par]Metis.. just a thought. :)