1. Department of Geochemistry, Institute of Rock Structure and Mechanics CAS, Prague 8, Czech Republic
2. Central Laboratories, University of Chemistry and Technology Prague, Prague 6, Czech Republic
3. Department of Research and Accreditted Prooving Laboratory, Bee Research Institute, Dol, Libčice nad Vltavou, Czech Republic
4. Faculty of Agrobiology, Food and Natural Resources, Department of Zoology and Fisheries, Czech University of Life Sciences Prague, Prague-Suchdol, Czech Republic