1. Black Hole Initiative, Harvard University, 20 Garden Street, Cambridge, MA 02138, USA
2. Center for Astrophysics, Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138, USA
3. Princeton Gravity Initiative, Princeton University, Jadwin Hall, Princeton, NJ 08544, USA
4. Tsung-Dao Lee Institute, Shanghai Jiao-Tong University, 520 Shengrong Road, Shanghai 201210, China
5. School of Physics & Astronomy, Shanghai Jiao-Tong University, 800 Dongchuan Road, Shanghai 200240, China
6. Institut für Theoretische Physik, Goethe-Universität Frankfurt, Max-von-Laue-Straße 1, D-60438 Frankfurt am Main, Germany
7. Institut für Theoretische Physik und Astrophysik, Universität Würzburg, Emil-Fischer-Str. 31, D-97074 Würzburg, Germany
8. Max–Planck–Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany
9. Technical University Munich (TUM), Boltzmannstr. 3, 85748 Garching, Germany
10. Max–Planck Institute for Astrophysics, Karl-Schwarzschild-Str. 1, 85748 Garching, Germany
11. Instituto de Astrofísica de Andalucía-CSIC, Glorieta de la Astronomía s/n, E-18008 Granada, Spain
12. Excellence Cluster ORIGINS, Boltzmannstr. 2, 85748 Garching, Germany
13. Moscow Institute of Physics and Technology, Institutsky per. 9, Dolgoprudny 141700, Russia
14. Lebedev Physical Institute of the Russian Academy of Sciences, Leninsky Prospekt 53, Moscow 119991, Russia
15. Department of Physics, Northeastern University, 360 Huntington Ave, Boston, MA 02115, USA