Depending on the version you are using, please, cite as follows:
M.J. Krause, N. Bogutzki, and A. Mink. OpenGPI Release 0.4: An Open and Generic Parameter Interface. Version 0.4. Mar. 2017. doi: 10.5281/zenodo.3629111. url: https://doi.org/10.5281/zenodo.3629111.
M.J. Krause, N. Bogutzki, and A. Mink. OpenGPI Release 0.3: An Open and Generic Parameter Interface. Version 0.3. Dec. 2016. doi: 10.5281/zenodo.3629104. url: https://doi.org/10.5281/zenodo.3629104.
M.J. Krause, J. Fietz, U. Zeltmann, M. Wlozka, M. Baumann, and H. Bockelmann. OpenGPI Release 0.2: An Open and Generic Parameter Interface. Version 0.2. Aug. 2010. doi: 10.5281/zenodo.3627128. url: https://doi.org/10.5281/zenodo.3627128.