Fabrication and Broadband Dielectric Study of Properties of Nanocomposites Materials Based on Polyurethane oleh Stefan Hardon, Jozef Kudelcik, Anton Baran, Pavel Trnka, Ondrej Michal, Adam Tamus, Tomasz Koltunowicz, Alena Kozakova, Tomas Derer, Jaroslav Hornak