GGOS-D: homogeneous reprocessing and rigorous combination of space geodetic observations. - Rothacher, M.; Angermann, D.; Artz, T.; Bosch, W.; Drewes, H.; Gerstl, M.; Kelm, R.; König, D.; König, R.; Meisel, B.; Müller, H.; Nothnagel, A.; et al. (Journal of Geodesy, 2011)