Sangin, S., and C. . Phonkusol. “Perception of Pregnancy Risk and Related Obstetric Factors Among Women of Advanced Maternal Age”. Pacific Rim International Journal of Nursing Research, vol. 25, no. 3, June 2021, pp. 494-0, https://he02.tci-thaijo.org/index.php/PRIJNR/article/view/248922.