1. Ghent University; Department of Archaeology; Sint-Pietersnieuwstraat 35 Ghent B-9000 Belgium
2. Charles University, Prague; Institute of Geochemistry, Mineralogy and Mineral Resources; Albertov 6 128 43 Prague 2 Czech Republic
3. Ghent University; Department of Analytical Chemistry; Krijgslaan 281 Ghent B-9000 Belgium