Affiliation: | (1) Central Economics and Mathematics Institute, Krasikova St. 32, 117418, Moscow, Russia, e-mail: cher@cher.msk.su. This work was done while the author worked for NEC Research Institute, Inc., RU;(2) NEC Research Institute, 4 Independence Way,Princeton, NJ 08540, USA. Current address: InterTrust Technology Corp., 460 Oakmead Parkway, Sunnyvale, CA 94086, USA, e-mail: goldberg@intertrust.com, URL: http://www.intertrust.com/star/goldberg/index.html, US |