Hassan, Murnihayati, et al. “High Unprotective Anti-HBs Antibodies Level Among Vaccinated Students in a Tertiary Teaching Hospital in North-Eastern Malaysia”. International Journal of Human and Health Sciences (IJHHS), vol. 3, no. 4, Sept. 2019, pp. 245-8, doi:10.31344/ijhhs.v3i4.111.