1. Institute of Geodesy and Geoinformation – IGG, University of Bonn, Nußallee 17, D-53115 Bonn, Germany
2. Max Planck Institute for Radio Astronomy, Auf dem Hügel 69, D-53121 Bonn, Germany
3. Owens Valley Radio Observatory, California Institute of Technology, Pasadena, CA 91125, USA
4. Tuorla Observatory, University of Turku, Väisäläntie 20, FI-21500 Piikkiö, Finland