1. Ultrasound and Non Destructive Testing Laboratory; Department of Electronics and Telecommunications; University of Florence; Via S. Marta, 3 50139 Firenze Italy
2. Remote Sensing Laboratory; Bauman Moscow State Technical University; Research Institute of Applied Mathematics and Mechanics; 2 Baumanskaya, 5 105005 Moscow Russia
3. Franklin and Marshall College; Department of Earth and Environment; Lancaster, PA 17604 USA
4. Enviroscan, Inc.; 1051 Columbia Avenue Lancaster, PA 17603 USA