1. Kaunas University of Technology, Baršausko st. 59, 51423 Kaunas, Lithuania
2. Ivan Franko National University of Lviv, Kyryla i Mefodiya 6, Lviv 79005, Ukraine
3. National University “Lviv Polytechnic”, Stepan Bandera 12, Lviv 79000, Ukraine
4. Institute of Low Temperature and Structure Research, Okólna 2, Wrocław 50-422, Poland