Degenerate soliton, breather and mixed solutions for a coupled Hirota–Maxwell–Bloch system in an erbium-doped fiberYun-Shan Xiao and Xi-Yang XieEur. Phys. J. Plus, 137 8 (2022) 937DOI: https://doi.org/10.1140/epjp/s13360-022-03131-6