Propagation characteristics of periodic structures possessing twist and polar glide symmetries Oskar Dahlberg, Fatemeh Ghasemifard, Guido Valerio and Oscar Quevedo-Teruel EPJ Appl. Metamat., 6 (2019) 14 Published online: 28 March 2019 DOI: 10.1051/epjam/2019012