Scattering of two and three physical pions at maximal isospin from lattice QCD - Extended Twisted Mass CollaborationMatthias Fischer, Bartosz Kostrzewa, Liuming Liu, Fernando Romero-López, Martin Ueding and Carsten UrbachEur. Phys. J. C, 81 5 (2021) 436DOI: https://doi.org/10.1140/epjc/s10052-021-09206-5