Chemical fingerprinting identifies Echium vulgare, Eupatorium cannabinum and Senecio spp. as plant species mainly responsible for pyrrolizidine alkaloids in bee-collected pollen - Kast, C; Kilchenmann, V; Reinhard, H; Droz, B; Lucchetti, M A; Dübecke, A; Beckh, G; Zoller, O (Food Addit Contam A, 2017)