2D Integrable systems, 4D Chern–Simons theory and affine Higgs bundles A. Levin, M. Olshanetsky and A. Zotov Eur. Phys. J. C, 82 7 (2022) 635 Published online: 23 July 2022 DOI: 10.1140/epjc/s10052-022-10553-0