00373nas a2200121   4500000000100000000000100001008004100002100003300043245009700076856006400173300000600237490000800243       2019                            d1 aet The EHT Collaboration al.00aFirst M87 Event Horizon Telescope Results. VI. The Shadow and Mass of the Central Black Hole  uhttps://iopscience.iop.org/article/10.3847/2041-8213/ab1141  a60 v875