Challenges from experiment: electronic structure of NiO C.-Y. Kuo, T. Haupricht, J. Weinen, Hua Wu, K.-D. Tsuei, M.W. Haverkort, A. Tanaka and L.H. Tjeng Eur. Phys. J. Special Topics, 226 11 (2017) 2445-2456 Published online: 10 July 2017 DOI: 10.1140/epjst/e2017-70061-7