Du, Z.X., et al. “Determination the Content of Plumbagin in Plumbago Zeylanica L. During Different Collected Periods by RP-HPLC”. Asian Journal of Chemistry, vol. 24, no. 5, Jan. 2012, pp. 2351-2, https://asianpubs.org/index.php/ajchem/article/view/9018.