1. Centre for Radio Cosmology, Department of Physics and Astronomy, University of the Western Cape, Cape Town 7535, South Africa
2. Centre for Radio Astronomy Techniques and Technologies, Department of Physics and Electronics, Rhodes University, PO Box 94, Grahamstown 6140, South Africa
3. South African Radio Astronomy Observatory, 3rd Floor, The Park, Park Road, Pinelands 7405, South Africa
4. Kapteyn Astronomical Institute, University of Groningen, PO Box 800, NL-9700 AV Groningen, the Netherlands
5. Ruđer Bošković Institute, Bijenička cesta 54, 10000 Zagreb, Croatia
6. ASTRON, PO Box 2, NL-7990 AA Dwingeloo, the Netherlands