Multiple cyclotron line-forming regions in GX 301−2 F. Fürst, S. Falkner, D. Marcu-Cheatham, B. Grefenstette, J. Tomsick, K. Pottschmidt, D. J. Walton, L. Natalucci and P. Kretschmar A&A, 620 (2018) A153 Published online: 11 December 2018 DOI: 10.1051/0004-6361/201732132