Ayan, Ali Kemal, et al. “Morphogenetic and Diurnal Variation of Total Phenols in Some <i>Hypericum< i> Species from Turkey During Their Phenological Cycles”. Bangladesh Journal of Botany, vol. 36, no. 1, Nov. 2008, pp. 39-46, doi:10.3329/bjb.v36i1.1547.