Prognostic relevance of a novel TNM classification system for upper gastroenteropancreatic neuroendocrine tumors - Pape, U F; Jann, H; Müller-Nordhorn, J; Bockelbrink, A; Berndt, U; Willich, S N; Koch, M; Röcken, C; Rindi, G; Wiedenmann, B (Cancer, 2008)