This author has not been identified. Look up 'Mihail Nedjalkov' in GoogleThis author has not been identified. Look up 'Paul Ellinghaus' in GoogleThis author has not been identified. Look up 'Josef Weinbub' in GoogleThis author has not been identified. Look up 'Toufik Sadi' in GoogleThis author has not been identified. Look up 'Asen Asenov' in GoogleThis author has not been identified. Look up 'Ivan Dimov' in GoogleThis author has not been identified. Look up 'Siegfried Selberherr' in Google