1. Faculty of Odonto - Stomatology, Hue University of Medicine and Pharmacy, Hue University, Thua Thien Hue, Vietnam.
2. Center of Population Health Sciences, Hanoi University of Public Health, Hanoi, Vietnam.
3. Faculty of Public Health, Hue University of Medicine and Pharmacy, Hue University, Thua Thien Hue, Vietnam.
4. Department of Biostatistics and Medical Informatics, Institute for Preventive Medicine and Public Health, Hanoi Medical University, Hanoi, Vietnam.