Robert Czech, Dariusz Wójcik, Tomasz Skweres, Wojciech Śliwiński, Dorota Zamkowska, Przemysław Ciepiela. "Maternal serum progesterone and BMI are associated with neonatal sex ratios following single frozen embryo transfer." PLoS ONE (2026). https://doi.org/10.1371/journal.pone.0346711