Kvaratskhelia, Natia, and Vasil Tkeshelashvili. “Multi-Causal Phenomenon of Preterm Delivery (Epidemiological Review)”. Caucasus Journal of Health Sciences and Public Health, vol. 1, no. 1, June 2017, pp. 36-43, https://caucasushealth.ug.edu.ge/index.php/caucasushealth/article/view/79.