Discovery of a gas-rich companion to the extremely metal-poor galaxy DDO 68

John M. Cannon, Megan Johnson, Kristen B.W. McQuinn, Erik D. Alfvin, Jeremy Bailin, H. Alyson Ford, Léo Girardi, Alec S. Hirschauer, Steven Janowiecki, John J. Salzer, Angela Van Sistine, Andrew Dolphin, E. C. Elson, Baerbel Koribalski, Paola Marigo, Jessica L. Rosenberg, Philip Rosenfield, Evan D. Skillman, Aparna Venkatesan, Steven R. Warren