https://www.researchgate.net/publication/238733155_Simultaneous_Determination_of_Five_Bioactive_Flavonoids_in_Hypericum_japonicum_Thunb_by_High-performance_Liquid_Chromatography (Any fulltext)
Li, J., Jiang, B., Liu, X., Zhang, J., Chen, H., & Bi, S. (2007). Simultaneous Determination of Five Bioactive Flavonoids in Hypericum japonicum Thunb by High-performance Liquid Chromatography. Asian Journal of Traditional Medicines, 2(2), 75-81.