Fractionation of polymeric procyanidins from lowbush blueberry and quantification of procyanidins in selected foods with an optimized normal-phase HPLC−MS fluorescent detection method - Gu, L; Kelm, M; Hammerstone, J F; Beecher, G; Cunningham, D; Vannozzi, S; Prior, R L (J Agric Food Chem, 2002)