Srisomboon, J., and T. Tongsong. “Pregnancy Outcome in Ederly Women Aged 35 Years or Older”. Thai Journal of Obstetrics and Gynaecology, vol. 6, no. 2, July 1994, pp. 121-7, https://he02.tci-thaijo.org/index.php/tjog/article/view/257782.