[1] Department of Electronic Devices,
[2] State University of Control Systems and Radioelectronics,undefined
[3] 40 Lenin Avenue,undefined
[4] Tomsk 634050,undefined
[5] Russia (Fax: +7-3822/414-321,undefined
[6] E-mail: shand@stack.ru),undefined
[7] Department of Physics,undefined
[8] University of Joensuu,undefined
[9] P.O. Box 111,undefined
[10] FIN-80101,undefined
[11] Joensuu,undefined
[12] Finland,undefined