1. B.P. Abbott et al. (LIGO Scientific, Virgo), Phys. Rev. Lett. 116, 061102 (2016). arXiv:1602.03837
2. B.P. Abbott et al. (LIGO Scientific, Virgo), Phys. Rev. X 9, 031040 (2019). arXiv:1811.12907
3. K. Akiyama et al. (Event Horizon Telescope), Astrophys. J. Lett. 875, L2 (2019). arXiv:1906.11239
4. K. Akiyama et al. (Event Horizon Telescope), Astrophys. J. Lett. 930, L12 (2022)
5. A.G. Riess et al. (Supernova Search Team), Astron. J. 116, 1009 (1998). arXiv:astro-ph/9805201