Ercisli, S., et al. “Determination of Elemental Variations in Tea Leaves (Camellia Sinensis L) in Different Harvest Time by WDXRF Spectrometry”. Asian Journal of Chemistry, vol. 21, no. 2, Mar. 2010, pp. 1313-7, https://asianpubs.org/index.php/ajchem/article/view/18826.