1. Institute of Geology and Mineralogy, Section Crystallography; University of Cologne; Greinstr. 6 50939 Köln Germany
2. Institute of Mineralogy and Crystallography; University of Vienna; Althanstr. 14 1090 Wien Austria
3. Institute of Geology and Mineralogy; Section Petrology; Greinstr. 4-6 50939 Köln Germany