Radiation collimation in a thick crystalline undulatorTobias Nyholm Wistisen, Ulrik Ingerslev Uggerhøj, John Lundsgaard Hansen, Werner Lauth and Pascal KlagEur. Phys. J. D, 71 5 (2017) 124DOI: https://doi.org/10.1140/epjd/e2017-70720-y