If the source of material obtained from this web site is not indicated otherwise, then the following reference should be included in any publication referring to material obtained here:
Plag, H.-P., Gross, R., Rothacher, M., 2009. Global Geodetic Observing System for Geohazards and Global Change. Geosciences, BRGM's journal for a sustainable Earth, 9, 96-103 (pdf).
If appropriate, reference can also be made to:
Plag, H.-P. & Pearlman, M., eds., 2009. Global Geodetic Observing System: Meeting the Requirements of a Global Society on a Changing Planet in 2020, Springer Berlin, 332 pages (http://www.springer.com/978-3-642-02686-7).