1. ASTRON, Netherlands Institute for Radio Astronomy, Oude Hoogeveensedijk 4, NL-7991 PD Dwingeloo, the Netherlands
2. Kapteyn Astronomical Institute, University of Groningen, PO Box 800, NL-9700 AV Groningen, the Netherlands
3. Department of Physics, University of Oxford, Keble Road, Oxford OX1 3RH, UK
4. Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK
5. European Southern Observatory, Karl-Schwarzschild-Str. 2, D-85748 Garching bei München, Germany
6. Science Support Office, ESTEC/SCI-S, Keplerlaan 1, NL-2201 AZ Noordwijk, the Netherlands
7. Departamento de Astronomía, Facultad Ciencias Físicas y Matemàticas, Universidad de Concepción, Av. Esteban Iturra s/n Barrio Universitario, Casilla 160-C Concepción, Chile
8. Leiden Observatory, Leiden University, PO Box 9513, NL-2300 RA Leiden, the Netherlands
9. Jodrell Bank Centre for Astrophysics, University of Manchester, Manchester M13 9PL, UK