1. Department of Nuclear Physics and Biophysics; Faculty of Mathematics, Physics and Informatics; Comenius University; SK-84248 Bratislava Slovakia
2. Department of Earth Sciences; ETH Zürich; CH-8092 Zürich Switzerland
3. Centre de Recherches Pétrographiques et Géochimiques; CNRS Nancy; F-54500 Vandœuvre les Nancy France
4. National Laboratory of Gran Sasso; INFN; I-67100 Assergi (AQ) Italy
5. Department of Astronomy; Physics of the Earth and Meteorology; Faculty of Mathematics; Physics and Informatics; Comenius University; SK-84248 Bratislava Slovakia
6. Astronomical Institute; Slovak Academy of Sciences; SK-84504 Bratislava Slovakia