1. Department of Mathematics, University of Toronto , 40 St. George Street, Toronto, ON M5S 2E4 , Canada
2. Radio Astronomy Laboratory , 501 Campbell Hall, University of California, Berkeley, CA 94720 , USA
3. SETI Institute , Mountain View, CA 94043 , USA
4. Department of Physics, University of Oxford , Denys Wilkinson Building, Keble Road, Oxford OX1 3RH , UK
5. Jodrell Bank Centre for Astrophysics, The University of Manchester , Manchester M13 9PL , UK
6. University of Malta, Institute of Space Sciences and Astronomy , L-Università ta' Malta Msida, MSD 2080 , Malta