This service has an associated publication. If you use its data, it may be appropriate to reference 2008A&A...488..401R (ADS BibTeX entry for the publication) either in addition to or instead of the service reference.
To cite the service as such, we suggest the following BibTeX entry:
@MISC{vo:ppmx_scs,
year=2007,
title={{PPMX} query},
author={Röser, S. and Schilbach, E. and Schwan, H. and Kharchenko, N.V. and Piskunov, A. and Scholz, R.},
url={https://dc.g-vo.org/ppmx/res/ppmx/scs/info},
howpublished={{VO} resource provided by the {GAVO} Data Center}
}