| Institute for Experimental Quantum Metrology (QUEST), Braunschweig, Germany | Piet Schmidt's group |
| PTB Working Group 4.44 Laser Nuclear Spectroscopy, Braunschweig, Germany | Ekkehard Peik's group |
| Helmholtz Institute Jena, Germany | Stephan Fritzsche's group |
| Helmholtz Institute Jena, Germany | Thomas Stöhlker's group |
| Technische Universität Darmstadt, Germany | Wilfried Nörtershäuser's group |
| GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany | Thomas Stöhlker's group |
| Helmholtz Institute Mainz, Germany | Dmitry Budker's group |
| ITMO University, Russia | Andrey Volotka |
| ITMO University, Russia | Dmitry Karlovets |
| Peter the Great St. Petersburg Polytechnic University, Russia | Vladimir Yerokhin's group |
| Novosibirsk State University, Russia | Valeriy Georgievich Serbo |
| Moscow State University, Russia | Alexei Grum-Grzhimailo |
| CERN, Switzerland | Mieczyslaw Witold Krasny |
| Taras Shevchenko National University of Kyiv, Ukraine | Alexander Yakimenko's group |
