Authors
S. Kovachov
Berdyansk State Pedagogical University, Berdyansk, UKRAINE
I. Bohdanov
Berdyansk State Pedagogical University, Berdyansk, UKRAINE
M. Konuhova
Institute of Solid State Physics, University of Latvia, Riga, LATVIA
A. I. Popov
Institute of Solid State Physics, University of Latvia, Riga, LATVIA