Staub, F.; Imesch, C.; Bleiner, D.; Balmer, J.E. (2012). Soft-X-ray lasing in nickel-like barium at 9.2 nm using the grazing-incidence scheme. Optics communications, 285(8), pp. 2118-2121. Amsterdam: Elsevier 10.1016/j.optcom.2011.12.077