How to cite open-code software for our research paper?
There are two ways to cite open-source software:
R:
R Development Core Team (2005). R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. ISBN 3-900051-07-0, URL http://www.R-project.org.
GRASS GIS:
GRASS Development Team (). Geographic Resources Analysis Support System (GRASS), GNU General Public License. http://grass.osgeo.org
Basically, you can use the available resources you find for that software. A link to the application's website or documentation page is all that's necessary.