Widyawati, F., B. Murti, and R. B. Adriani. “Meta-Analysis: The Effect of Prenatal Yoga and the Use of Transcutanal Electric Nerve Stimulation During Pregnancy on Labor Pain”. Journal of Maternal and Child Health, vol. 6, no. 5, Sept. 2021, pp. 547-59, https://thejmch.com/index.php/thejmch/article/view/673.