We are grateful to our sponsors:

	Excellence Center of Advanced Materials Research and Technology (CAMART) (2002)
	Institute of Solid State Physics (ISSP) (2002 - ...)
	University of Latvia (2003 - ...)
	ESF project (2009/0202/1DP/1.1.1.2.0/09/APIA/VIAA/141) (2009-2012)
	University Duisburg-Essen (2013)
	ERDF project 2.1.1.3.2 (2015)
	ERDF project 1.1.1.4/17/I/002 (2017-2021)