Comparison of the Effect of Nifedipine Alone and the Combination of Nifedipine and Sildenafil in Delaying Preterm Labor: A Randomized Clinical Trial - Mohammadi, Elham; Noei Teymoordash, Somayyeh; Norouzi, Ali; Norouzi, Fatemeh; Norouzi, Hamid (Journal of Family and Reproductive Health, 2021)