Application of groundwater quality index (GWQI) and GIS in groundwater quality zoing in Pleistocene aquifer in Phu My town, Ba Ria – Vung Tau province - Nguyen, Au; Pham, Nhi; Tat, Vy; Truong, Hien; Tran, Hiep; Luu, Linh; Tran, Bao; Luong, Ha (VNUHCM Journal of Environment and Earth Sciences, 2020)