One-Sign Order Parameter in Iron Based Superconductor. - Sergey V. Borisenko; Volodymyr B. Zabolotnyy; Alexnader A. Kordyuk; Danil V. Evtushinsky; Timur K. Kim; Igor V. Morozov; Rolf Follath; Bernd Büchner (Symmetry, 2012)