The nature of the X-ray sources constituting the 6.7 keV Galactic ridge emission J. H. M. M. Schmitt, S. Czesla, P. C. Schneider, S. Freund and J. Robrade A&A, 661 (2022) A88 Published online: 05 May 2022 DOI: 10.1051/0004-6361/202142876