Treatment of nasopharyngeal carcinoma in children and adolescents: definitive results of a multicenter study (NPC-91-GPOH) - Mertens, R; Granzen, B; Lassay, L; Bucsky, P; Hundgen, M; Stetter, G; Heimann, G; Weiss, C; Hess, C F; Gademann, G (Cancer, 2005)