The authors introduce the GRASS GIS add-on module g.citation. The module extends the existing citationcapabilities of GRASS GIS, which until now only provide for automated citation of the software projectas a whole, authored by the GRASS Development Team, without reference to individual persons. Thefunctionalities of the new module enable individual code citation for each of the over 500 implementedfunctionalities, including add-on modules. Three different classes of citation output are provided in avariety human- and machine-readable formats. The implications of this reference implementation ofscientific software citation for both for the GRASS GIS project and the OSGeo foundation are outlined.