1. Finnish Geodetic Institute; Geodeetinrinne 2, P.O. Box 15 Masala FI-02431 Finland
2. Department of Computational Physics; Dorodnicyn Computing Centre; Russian Academy of Sciences; Vavilova ul. 40 Moscow 119333 Russia
3. Institute of Mechanics; Lomonosov Moscow State University; Michurinsky prt., 1 Moscow 119192 Russia
4. Department of Physics; University of Helsinki; P.O. Box 64 Helsinki 00014 Finland
5. Institute of Geology; Academy of Sciences of the Czech Republic; Rozvojová 269 Prague 6 16500 Czech Republic
6. Faculty of Mathematics, Physics and Informatics; Comenius University; Mlynská dolina Bratislava SK-84248 Slovakia