Donel S. et al. 2022. Seroprevalence of Anti-SARS-CoV-2 Among Pregnant Women Prior to COVID-19 Vaccination in Pekanbaru, Riau. Nusantara Science and Technology Proceedings. (Dec. 2022), 70–72. DOI:https://doi.org/10.11594/nstp.2022.2813.