Occurrence of Neurotoxic 4′-O-Methylpyridoxine in Ginkgo biloba Leaves, Ginkgo Medications and Japanese Ginkgo Food - Arenz, Ansgar; Klein, Matthias; Fiehe, Katrin; Groß, Julia; Drewke, Christel; Hemscheidt, Thomas; Leistner, Eckhard (Planta Medica, 1996)