Starbova, K. [P:(DE-Juel1)VDB5995] ; Mankov, V. [P:(DE-HGF)0] ; Starbov, N. [P:(DE-Juel1)VDB5992] ; Popov, D. [P:(DE-HGF)0] ; Nihtianova, D. [P:(DE-HGF)0] ; Kolev, D. [P:(DE-HGF)0] ; Laude, L. D. [P:(DE-HGF)0]