Petrova, N., E. Hristova, M. Hristova, and P. Todorov. “Investigating the Relationship Between the Day of Embryo Freezing and Pregnancy Rates”. Proceedings of the Bulgarian Academy of Sciences, vol. 75, no. 12, Dec. 2022, pp. 1749-56, doi:10.7546/CRABS.2022.12.06.