Association between pre-diagnostic circulating vitamin D concentration and risk of colorectal cancer in European populations: a nested case-control study - Jenab, M; Bueno-de-Mesquita, HB; Ferrari, P; van, Duijnhoven FJB; Norat, T; Pischon, T; Jansen, EHJM; Slimani, N; Byrnes, G; Rinaldi, S; Tjonneland, A; Olsen, A; et al. (British Medical Journal, 2010)