Multiple retrograde substructures in the Galactic halo: A shattered view of Galactic history Helmer H. Koppelman, Amina Helmi, Davide Massari, Adrian M. Price-Whelan and Tjitske K. Starkenburg A&A, 631 (2019) L9 Published online: 13 November 2019 DOI: 10.1051/0004-6361/201936738