Niobium near-surface composition during nitrogen infusion relevant for superconducting radio-frequency cavities oleh G. D. L. Semione, A. Dangwal Pandey, S. Tober, J. Pfrommer, A. Poulain, J. Drnec, G. Schütz, T. F. Keller, H. Noei, V. Vonk, B. Foster, A. Stierle