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Elliott, JP (децембар 2008). „Preterm labor in twins and high-order multiples”. Clinical Perinatology. 34 (4): 599—609. PMID18063108. doi:10.1016/j.clp.2007.10.004. „Unlike singleton gestation where identification of patients at risk for PTL is often difficult, every multiple gestation is at risk for PTL, so all patients can be managed as being at risk.”CS1 одржавање: Формат датума (веза)
emedicine.com
Zach, Terence; Arun K Pramanik; Susannah P Ford (2007-10-02). „Multiple Births”. WebMD. Приступљено 2008-09-29.
Elliott, JP (децембар 2008). „Preterm labor in twins and high-order multiples”. Clinical Perinatology. 34 (4): 599—609. PMID18063108. doi:10.1016/j.clp.2007.10.004. „Unlike singleton gestation where identification of patients at risk for PTL is often difficult, every multiple gestation is at risk for PTL, so all patients can be managed as being at risk.”CS1 одржавање: Формат датума (веза)