1. Physikalisch-Technische Bundesanstalt (PTB)
2. 38116 Braunschweig
3. Germany
4. National Physical Laboratory
5. Analytical Science Division
6. Teddington
7. UK
8. Centre for Isotope Research (CIO)
9. Energy and Sustainability Institute Groningen (ESRIG)
10. University of Groningen
11. Groningen
12. The Netherlands