What is the Milky Way outer halo made of? - High resolution spectroscopy of distant red giantsG. Battaglia, P. North, P. Jablonka, M. Shetrone, D. Minniti, M. Díaz, E. Starkenburg and M. SavoyA&A, 608 (2017) A145DOI: https://doi.org/10.1051/0004-6361/201731879