Preliminary Identification and Quantification of Four Secondary Metabolites, Total Tannin and Total Flavonoid Contents in Guava Fruit Ethanol Extract, Dhianawaty, Diah, Atik Nur, Dwiwina Resti Gradia, and Muda Iskandar , Pharmacognosy Journal, April 2022, Volume 14, Issue 2, p.350-357, (2022)