1. B. Abbott et al. (LIGO Scientific and Virgo), Observation of gravitational waves from a binary black hole merger. Phys. Rev. Lett. 116(6), 061102 (2016). arXiv:1602.03837 [gr-qc]
2. B.P. Abbott et al. (LIGO Scientific and Virgo), GW151226: observation of gravitational waves from a 22-solar-mass binary black hole coalescence. Phys. Rev. Lett. 116(24), 241103 (2016). arXiv:1606.04855 [gr-qc]
3. B.P. Abbott et al. (LIGO Scientific and Virgo), GW170608: observation of a 19-solar-mass binary black hole coalescence. Astrophys. J. 851(2), L35 (2017). arXiv:1711.05578 [astro-ph.HE]
4. K. Akiyama et al. (Event Horizon Telescope), First M87 event horizon telescope results. I. The shadow of the supermassive black hole. Astrophys. J. Lett. 875, L1 (2019). arXiv:1906.11238 [astro-ph.GA]
5. L. Barack, V. Cardoso, S. Nissanke, T.P. Sotiriou, A. Askar, C. Belczynski, G. Bertone, E. Bon, D. Blas, R. Brito et al., Black holes, gravitational waves and fundamental physics: a roadmap. Class. Quantum Gravity 36(14), 143001 (2019). arXiv:1806.05195 [gr-qc]