Yan, Y.Z., J.C. Xue, J.R. Wu, D.S. Yoo, S.Y. Lee, Y.K. Kim, M.R. Uddin, and S.U. Park. 2011. “Variation of Triterpenoid Saponin Content in Platycodon Grandiflorum (Jacq.) A.D.C”. Asian Journal of Chemistry 24 (3):1268-70. https://asianpubs.org/index.php/ajchem/article/view/8755.