Broadband X-ray observations of four gamma-ray narrow-line Seyfert 1 galaxies M. Berton, V. Braito, S. Mathur, L. Foschini, E. Piconcelli, S. Chen and R. W. Pogge A&A, 632 (2019) A120 Published online: 16 December 2019 DOI: 10.1051/0004-6361/201935929