Inayat, A., S. R. Khan, M. N. Chowdhry, and A. Waheed. “Analysis of Caffeine and Heavy Metal Contents in Branded and Unbranded Tea Available in Pakistan: Caffeine and Heavy Metals in Tea”. Biological Sciences - PJSIR, vol. 53, no. 1, Feb. 2010, pp. 20-24, https://v2.pjsir.org/index.php/biological-sciences/article/view/414.