1. .N. Karazin Kharkov State University, Kharkov, Ukraine
2. A.Ya. Usikov Institute for Radio-Physics and Electronics, National Academy of Sciences of the Ukraine, Kharkov, Ukraine
3. CAESAR Consultancy, Cambridge, United Kingdom; University of Bath, Department of Electronic and Electrical Engineering, Bath, United Kingdom
4. Institute of Geophysics, Polish Academy of Sciences, Warsaw, Poland