**6. Acknowledgements**

*In memoriam of professor Yuriy M. Petrusevich (1935-2010).* 

I would like to thank my colleagues Yu.M. Petrusevich, K.V. Fedorova, M.A.Gurova, M.S. Ivanova, V.P. Khlapov, A.M. Makurenkov, I.A. Sergeeva, T.N. Tikhonova, E.A.Papish, N.V.Sokol for taking part in these investigations.
