1. Department of Physical and Chemical Sciences University of L'Aquila L'Aquila Italy
2. The Johns Hopkins University Applied Physics Laboratory Laurel MD USA
3. Helmholtz Centre Potsdam GFZ German Research Centre for Geosciences and University of Potsdam Potsdam Germany
4. Space Science and Engineering Division Southwest Research Institute San Antonio TX USA
5. University of Alberta Edmonton AB Canada
6. Institute of Geophysics Polish Academy of Sciences Warsaw Poland
7. Mining and Geological Survey of Hungary Budapest Hungary
8. Eötvös Loránd University Budapest Hungary