Vitamin D deficiency and a CYP27B1–1260 promoter polymorphism are associated with chronic hepatitis C and poor response to interferon-alfa based therapy - Lange, CM; Bojunga, J; Ramos-Lopez, E; Wagner, M von; Hassler, A; Vermehren, J; Herrmann, E; Badenhoop, K; Zeuzem, S; Sarrazin, C (Zeitschrift für Gastroenterologie, 2010)