00350nas a2200121   4500000000100000000000100001008004100002100002900043245007700072856006400149300000700213490000800220       2021                            d1 aet EHT Collaboration al.00aFirst M87 Event Horizon Telescope Results. VII. Polarization of the Ring  uhttps://iopscience.iop.org/article/10.3847/2041-8213/abe71d  a480 v910