K. Letchumanan, N.H. Abdullah, M.M. Pisar, H.M. Ismail, R. Kadir, A. Abdul-Aziz, Application of Response Surface Methodology for the Optimization of the Extraction of Triterpenoid Saponins from Azadirachta excelsa Leaves, Chemical Engineering Transactions. 106 (2023) 1159-1164. doi:10.3303/CET23106194.