\begin{thebibliography}{22}
\expandafter\ifx\csname natexlab\endcsname\relax\def\natexlab#1{#1}\fi

\bibitem[\protect\citename{Beutler et~al., }2003]{beutler++2003}
Beutler, G., Drewes, H., Reigber, C., \& Rummel, R., 2003. {Proposal to
  Establish the Integrated Global Geodetic Observing System (IGGOS) as IAG's
  First Project}, distributed to IVS and IGS mailing lists on 21 August 2003.

\bibitem[\protect\citename{Beutler et~al., }2005]{beutler++2005}
Beutler, G., Drewes, H., Plag, H.-P., Reigber, C., Rothacher, M., \& Rummel,
  R., 2005. {IAG GGOS Implementation Plan}, Tech. rep., GeoForschungZentrum
  Potsdam, Germany.

\bibitem[\protect\citename{Drewes, }2006]{drewes2006}
Drewes, H., 2006. The science rationale of the {Global Geodetic Observing
  System} {GGOS}, in {\em Dynamic Planet -- Monitoring and Understanding a
  Dynamic Planet with Geodetic and Oceanographic Tools\/}, edited by
  P.~Tregoning \& C.~Rizos, vol. 130 of {\bf International Association of
  Geodesy Symposia}, pp. 703--710, Springer Verlag, Berlin.

\bibitem[\protect\citename{Gross et~al., }2007]{gross++2007}
Gross, R., Beutler, G., \& Plag, H.-P., 2007. Integrated scientific and
  societal user requirements and functional specifications for the ggos, in
  {\em The Global Geodetic Observing System: Meeting the Requirements of a
  Global Society on a Changing Planet in 2020 -- The Reference Document\/},
  edited by H.-P. Plag \& M.~Pearlman, Global Geodetic Observing System,
  available at http://geodesy.unr.edu/ggos/ggos2020/.

\bibitem[\protect\citename{Herring et~al., }2007]{herring++2007}
Herring, T.~A., Altamimi, Z., Plag, H.-P., Poli, P., \& Ray, J., 2007. The
  future geodetic reference frame, in {\em The Global Geodetic Observing
  System: Meeting the Requirements of a Global Society on a Changing Planet in
  2020 -- The Reference Document\/}, edited by H.-P. Plag \& M.~Pearlman,
  Global Geodetic Observing System, available at
  http://geodesy.unr.edu/ggos/ggos2020/.

\bibitem[\protect\citename{Pearlman et~al., }2006]{pearlman++2006}
Pearlman, M., Altamimi, Z., Beck, N., Forsberg, R., Gurtner, W., Kenyon, S.,
  Behrend, D., Lemoine, F.~G., Ma, C., Noll, C.~E., Pavlis, E.~C., Malkin, Z.,
  Moore, A.~W., Webb, F.~H., Neilan, R.~E., Ries, J.~C., Rothacher, M., \&
  Willis, P., 2006. {GGOS Working Group on} ground networks and communications,
  in {\em Dynamic Planet -- Monitoring and Understanding a Dynamic Planet with
  Geodetic and Oceanographic Tools\/}, edited by P.~Tregoning \& C.~Rizos, vol.
  130 of {\bf International Association of Geodesy Symposia}, pp. 719--726,
  Springer Verlag, Berlin.

\bibitem[\protect\citename{Pearlman et~al., }2007]{pearlman++2007}
Pearlman, M., Altamimi, Z., Beck, N., Forsberg, R., Gurtner, W., Kenyon, S.,
  Behrend, D., Lemoine, F., Ma, C., Noll, C.~E., Pavlis, E.~C., Malkin, Z.,
  Moore, A.~W., Webb, F.~H., Neilan, R.~E., Ries, J.~C., Rothacher, M., \&
  Willis, P., 2007. {Global Geodetic Observing System - Considerations for the
  Geodetic Network Infrastructure}, {\it Geomatica\/}, {\bf 60}(2), 193--204.

\bibitem[\protect\citename{Plag, }2005{\natexlab{a}}]{plag2005a}
Plag, H.-P., 2005. The {GGOS} as the backbone for global observing and local
  monitoring: a user driven perspective, {\it J.\ Geodynamics\/}, {\bf 40},
  479--486, doi:10.1016/j.jog.2005.06.012.

\bibitem[\protect\citename{Plag, }2005{\natexlab{b}}]{plag2005j}
Plag, H.-P., 2005. The {Global Geodetic Observing System and how it relates to
  IGOS Geohazards}, in {\em IGOS Geohazards Workshop, 27-29 June 2005, Orleans,
  France: Programme and Abstracts\/}, pp. Abstract, invited presentation.

\bibitem[\protect\citename{Plag, }2006]{plag2006f}
Plag, H.-P., 2006. {GGOS} and it user requirements, linkage and outreach, in
  {\em Dynamic Planet -- Monitoring and Understanding a Dynamic Planet with
  Geodetic and Oceanographic Tools\/}, edited by P.~Tregoning \& C.~Rizos, vol.
  130 of {\bf International Association of Geodesy Symposia}, pp. 711--718,
  Springer Verlag, Berlin.

\bibitem[\protect\citename{Plag \& Rothacher, }2006]{plag+rot2006}
Plag, H.-P. \& Rothacher, M., 2006. {Earth System Dynamics: Toward a Theme
  proposal initiated by the Global Geodetic Observing System (GGOS) of the
  International Association of Geodesy (IAG)}, Presentation at IGOS-P-13,
  Geneva, May 2006.

\bibitem[\protect\citename{Plag et~al., }2005{\natexlab{a}}]{plag++2005g}
Plag, H.-P., Beutler, G., Forsberg, R., Ma, C., Neilan, R., Pearlman, M.,
  Richter, B., \& Zerbini, S., 2005. The {Global Geodetic Observing System
  (GGOS)}: observing the dynamics of the {E}arth system, Available at
  http://www.unep.org/dewa/igos.

\bibitem[\protect\citename{Plag et~al., }2005{\natexlab{b}}]{plag++2005p}
Plag, H.-P., Willis, P., Richter, B., \& Altamimi, Z., 2005. Identification,
  quality control, copyright and certification issues associated with ggos
  products, Position paper prepared for First GGOS Workshop, March 1-2, 2005,
  Potsdam, Germany. Available at http://geodesy.unr.edu/ggos\_plmwg/.

\bibitem[\protect\citename{Plag et~al., }2006{\natexlab{a}}]{plag++2006h}
Plag, H.-P., Beutler, G., Forsberg, R., Ma, C., Neilan, R., Pearlman, M.,
  Richter, B., \& Zerbini, S., 2006. Linking the {Global Geodetic Observing
  System (GGOS)} to the {Integrated Global Observing Strategy Partnership
  (IGOS-P)} through the {Theme 'Earth System Dynamics'}, in {\em Dynamic Planet
  -- Monitoring and Understanding a Dynamic Planet with Geodetic and
  Oceanographic Tools\/}, edited by P.~Tregoning \& C.~Rizos, vol. 130 of {\bf
  International Association of Geodesy Symposia}, pp. 727--734, Springer
  Verlag, Berlin.

\bibitem[\protect\citename{Plag et~al., }2006{\natexlab{b}}]{plag++2006s}
Plag, H.-P., Rothacher, M., Gross, R., \& Bettadpur, S., 2006. {The Global
  Geodetic Observing System (GGOS) of the International Association of Geodesy
  (IAG)}, Presentation at IGOS-P Theme Leader Meeting, Geneva, May 2006.

\bibitem[\protect\citename{Plag et~al., }2007{\natexlab{a}}]{plag++2007}
Plag, H.-P., Altamimi, Z., Bettadpur, S., Beutler, G., Beyerle, G., Cazenave,
  A., Crossley, D., Donnellan, A., Forsberg, R., Gross, R., Hinderer, J.,
  Komjathy, A., Mannucci, A.~J., Ma, C., Noll, C., Nothnagel, A., Pavlis,
  E.~C., Pearlman, M., Poli, P., Schreiber, U., Senior, K., Woodworth, P., \&
  Zuffada, C., 2007. The goals, achievements, and tools of modern geodesy, in
  {\em The Global Geodetic Observing System: Meeting the Requirements of a
  Global Society on a Changing Planet in 2020 -- The Reference Document\/},
  edited by H.-P. Plag \& M.~Pearlman, Global Geodetic Observing System,
  available at http://geodesy.unr.edu/ggos/ggos2020/.

\bibitem[\protect\citename{Plag et~al., }2007{\natexlab{b}}]{plag++2007a}
Plag, H.-P., Blewitt, G., \& Herring, T.~A., 2007. Towards a consistent
  conventional treatment of surface-load induced deformations, Position Paper
  presented at the IERS Workshop on Conventions, September 20-21, 2007, Sevres,
  France. Available at http://www.bipm.org/en/events/iers/papers.html.

\bibitem[\protect\citename{Poutanen et~al., }2005]{poutanen++2005a}
Poutanen, M., Knudsen, P., Lilje, M., Plag, H.-P., \& Scherneck, H.-G., 2005.
  Ngos - {The Nordic Geodetic Observing System}, {\it nordic journal\/}, {\bf
  2}, 77--98.

\bibitem[\protect\citename{Poutanen et~al., }2006]{poutanen++2006}
Poutanen, M., Knudsen, P., Lilje, M., Norbech, T., Plag, H.-P., \& Scherneck,
  H.-G., 2006. The nordic geodetic observing system, in {\em Dynamic Planet --
  Monitoring and Understanding a Dynamic Planet with Geodetic and Oceanographic
  Tools\/}, edited by P.~Tregoning \& C.~Rizos, vol. 130 of {\bf International
  Association of Geodesy Symposia}, pp. 749--756, Springer Verlag, Berlin.

\bibitem[\protect\citename{Rummel, }2000]{rummel2000}
Rummel, R., 2000. {Global Integrated Geodetic and Geodynamic Observing System
  (GIGGOS)}, in {\em Towards an Integrated Global Geodetic Observing System\/},
  edited by R.~Rummel, H.~Drewes, W.~Bosch, \& H.~Hornik, vol. 120 of {\bf
  International Association of Geodesy Symposia}, pp. 253--260, Springer,
  Berlin.

\bibitem[\protect\citename{Rummel et~al., }2002]{rummel++2002}
Rummel, R., Drewes, H., \& Beutler, G., 2002. {Integrated Global Geodetic
  Observing System (IGGOS): A candidate IAG project}, in {\em Vistas for
  Geodesy in the New Millennium\/}, edited by J.~Adam \& K.-P. Schwarx, vol.
  125 of {\bf International Association of Geodesy Symposia}, pp. 609--614,
  Springer, Berlin.

\bibitem[\protect\citename{Rummel et~al., }2005]{rummel++2005}
Rummel, R., Rothacher, M., \& Beutler, G., 2005. {Global Geodetic Observing
  System (GGOS): Science rationale}, {\it J.\ Geodynamics\/}, {\bf 40},
  357--362.

\end{thebibliography}