Event Horizon Telescope Collaboration;Akiyama, Kazunori;Alberdi, Antxon;Alef, Walter;Asada, Keiichi;Azulay, Rebecca;Baczko, Anne-Kathrin;Ball, David;Baloković, Mislav;Barrett, John;Bintley, Dan;Blackburn, Lindy;Boland, Wilfred;Bouman, Katherine L.;Bower, Geoffrey C.;Bremer, Michael;Brinkerink, Christiaan D.;Brissenden, Roger;Britzen, Silke;Broderick, Avery E.;Broguiere, Dominique;Bronzwaer, Thomas;Byun, Do-Young;Carlstrom, John E.;Chael, Andrew;Chan, Chi-kwan;Chatterjee, Shami;Chatterjee, Koushik;Chen, Ming-Tang;Chen, Yongjun;Cho, Ilje;Christian, Pierre;Conway, John E.;Cordes, James M.;Crew, Geoffrey B.;Cui, Yuzhu;Davelaar, Jordy;De Laurentis, Mariafelicia;Deane, Roger;Dempsey, Jessica;Desvignes, Gregory;Dexter, Jason;Doeleman, Sheperd S.;Eatough, Ralph P.;Falcke, Heino;Fish, Vincent L.;Fomalont, Ed;Fraga-Encinas, Raquel;Friberg, Per;Fromm, Christian M.;Gómez, José L.;Galison, Peter;Gammie, Charles F.;García, Roberto;Gentaz, Olivier;Georgiev, Boris;Goddi, Ciriaco;Gold, Roman;Gu, Minfeng;Gurwell, Mark;Hada, Kazuhiro;Hecht, Michael H.;Hesper, Ronald;Ho, Luis C.;Ho, Paul;Honma, Mareki;Huang, Chih-Wei L.;Huang, Lei;Hughes, David H.;Ikeda, Shiro;Inoue, Makoto;Issaoun, Sara;James, David J.;Jannuzi, Buell T.;Janssen, Michael;Jeter, Britton;Jiang, Wu;Johnson, Michael D.;Jorstad, Svetlana;Jung, Taehyun;Karami, Mansour;Karuppusamy, Ramesh;Kawashima, Tomohisa;Keating, Garrett K.;Kettenis, Mark;Kim, Jae-Young;Kim, Junhan;Kim, Jongsoo;Kino, Motoki;Koay, Jun Yi;Koch, Patrick M.;Koyama, Shoko;Kramer, Michael;Kramer, Carsten;Krichbaum, Thomas P.;Kuo, Cheng-Yu;Lauer, Tod R.;Lee, Sang-Sung;Li, Yan-Rong;Li, Zhiyuan;Lindqvist, Michael;Liu, Kuo;Liuzzo, Elisabetta;Lo, Wen-Ping;Lobanov, Andrei P.;Loinard, Laurent;Lonsdale, Colin;Lu, Ru-Sen;MacDonald, Nicholas R.;Mao, Jirong;Markoff, Sera;Marrone, Daniel P.;Marscher, Alan P.;Martí-Vidal, Iván;Matsushita, Satoki;Matthews, Lynn D.;Medeiros, Lia;Menten, Karl M.;Mizuno, Yosuke;Mizuno, Izumi;Moran, James M.;Moriyama, Kotaro;Moscibrodzka, Monika;Müller, Cornelia;Nagai, Hiroshi;Nagar, Neil M.;Nakamura, Masanori;Narayan, Ramesh;Narayanan, Gopal;Natarajan, Iniyan;Neri, Roberto;Ni, Chunchong;Noutsos, Aristeidis;Okino, Hiroki;Olivares, Héctor;Oyama, Tomoaki;Özel, Feryal;Palumbo, Daniel C. M.;Patel, Nimesh;Pen, Ue-Li;Pesce, Dominic W.;Piétu, Vincent;Plambeck, Richard;PopStefanija, Aleksandar;Porth, Oliver;Prather, Ben;Preciado-López, Jorge A.;Psaltis, Dimitrios;Pu, Hung-Yi;Ramakrishnan, Venkatessh;Rao, Ramprasad;Rawlings, Mark G.;Raymond, Alexander W.;Rezzolla, Luciano;Ripperda, Bart;Roelofs, Freek;Rogers, Alan;Ros, Eduardo;Rose, Mel;Roshanineshat, Arash;Rottmann, Helge;Roy, Alan L.;Ruszczyk, Chet;Ryan, Benjamin R.;Rygl, Kazi L. J.;Sánchez, Salvador;Sánchez-Arguelles, David;Sasada, Mahito;Savolainen, Tuomas;Schloerb, F. Peter;Schuster, Karl-Friedrich;Shao, Lijing;Shen, Zhiqiang;Small, Des;Sohn, Bong Won;SooHoo, Jason;Tazaki, Fumie;Tiede, Paul;Tilanus, Remo P. J.;Titus, Michael;Toma, Kenji;Torne, Pablo;Trent, Tyler;Trippe, Sascha;Tsuda, Shuichiro;van Bemmel, Ilse;van Langevelde, Huib Jan;van Rossum, Daniel R.;Wagner, Jan;Wardle, John;Weintroub, Jonathan;Wex, Norbert;Wharton, Robert;Wielgus, Maciek;Wong, George N.;Wu, Qingwen;Young, André;Young, Ken;Younsi, Ziri;Yuan, Feng;Yuan, Ye-Fei;Zensus, J. Anton;Zhao, Guangyao;Zhao, Shan-Shan;Zhu, Ziyan;Farah, Joseph R.;Meyer-Zhao, Zheng;Michalik, Daniel;Nadolski, Andrew;Nishioka, Hiroaki;Pradel, Nicolas;Primiani, Rurik A.;Souccar, Kamal;Vertatschitsch, Laura;Yamaguchi, Paul