M. Aaboud, G. Aad, B. Abbott, O. Abdinov, B. Ali, K. Augsten, D. Caforio, P. Gallus, M. Havránek, Z. Hubáček et al.: Measurement of the production cross section of three isolated photons in pp collisions at root s=8 TeV using the ATLAS detector. Physics Letters B 781, 55-76 (2018). doi:10.1016/j.physletb.2018.03.057