A. Saletra-Bielińska, K. Kosińska-Kaczyńska, I. Szymusik, J. Niderla-Bielińska, J. Malejczyk, and M. Wielgoś, “Cervical expression of elafin and secretory leukocyte peptidase inhibitor does not predict preterm delivery in twin pregnancy – results from a pilot study”, JMS, vol. 90, no. 1, p. e490, Feb. 2021, doi: 10.20883/medical.e490.