This study was supported by the International Visegrad fund scholarship (RZ: #50910830) and the grant (RZ: # ECSP-09-70) of the State Committee of Science of the Ministry of Education and Science of RA and the National Foundation of Science and Advanced Technologies (RA). This work was also supported in part by Palacky University (IGA PU LF 2010_08) and Czech governmental funding (MSM 6198959205).