Yashin, A. Y. “Determination Theaflavins in Black Teas of the Different Countries by HPLC Method With Amperometric Detector”. Sorbtsionnye I Khromatograficheskie Protsessy, Vol. 20, no. 2, May 2020, pp. 158-65, doi:10.17308/sorpchrom.2020.20/2770.