Affiliation: | a Department of Glass and Ceramics, Institute of Chemical Technology, Prague, Technická 5, 166 28 Prague 6, Czech Republic b Department of Inorganic Technology, Institute of Chemical Technology, Prague, Technická 5, 166 28 Prague 6, Czech Republic c Institute of Rock Structure and Mechanics, Academy of Sciences of the Czech Republic, V Holešovi?kách 41, 182 09 Prague 8, Czech Republic |