Swift/XRT counterparts to unassociated Fermi high-energy LAT sources R. Landi, L. Bassani, J. B. Stephen, N. Masetti, A. Malizia and P. Ubertini A&A, 581 (2015) A57 Published online: 01 September 2015 DOI: 10.1051/0004-6361/201526221