Plasma levels of six carotenoids in nine European countries: report from the European Prospective Investigation into Cancer and Nutrition (EPIC). by Al-Delaimy, W, van Kappel, A, Ferrari, P, Slimani, N, Steghens, J, Bingham, S, Johansson, I, Wallström, P, Overvad, K, Tjønneland, A, Key, T, Welch, A, Bueno-de-Mesquita, H, Peeters, P, Boeing, H, Linseisen, J, Clavel-Chapelon, F, Guibout, C, Navarro, C, Quirós, JR, Palli, D, Celentano, E, Trichopoulou, A, Benetou, V, Kaaks, R