1. DIEI, Università degli Studi di Cassino e del Lazio Meridionale, via G. Di Biasio 43, 03043 Cassino (FR), Italy
2. Institut Camille Jordan UMR, CNRS 5208, Université de Lyon/Université de Saint Etienne, 23, rue P. Michelon, 42023 St. Etienne, France
3. Narvik University College, HiN, Postbox 385, 8505 Narvik, Norway
4. P. N. Lebedev Physical Institute RAS, 53 Leninski Prospect, Moscow 119991, Russia