Wawryków, Agata, and Katarzyna Korabiusz. “Transcutaneous Electrical Nerve Stimulation As a Method to Relieve Pain During Childbirth”. Journal of Education, Health and Sport, vol. 8, no. 9, Sept. 2018, pp. 543-8, https://apcz.umk.pl/JEHS/article/view/5923.