Three New Tazettine-Type Alkaloids from Galanthus gracilis and Galanthus plicatus Subsp. byzantinus - Ünver, Nehir; Noyan, Seda; Gözler, Tekant; Önür, Mustafa Ali; Gözler, Belkıs; Hesse, Manfred (Planta Medica, 1999)