1. Department of Physics; Sultan Qaboos University; PC 123 Muscat Oman
2. Department of Physics; University of Khartoum; Khartoum 11115 Sudan
3. Department of Geological Sciences; University of Manitoba; Winnipeg Manitoba R3T 2N2 Canada
4. Department of Physics; IIT Kanpur; Kanpur 208016 India
5. SETI Institute; Carl Sagan Center; Mountain View California 94043 USA