Viana CHC, Silveira PRS da, Moretti AS, Rodrigues PHM. Relationships between the characteristics weaning-to-estrus interval, estrus duration and moment of ovulation by ultrasonography in sows. Braz. J. Vet. Res. Anim. Sci. 1999;36(4):212-218. doi:10.1590/S1413-95961999000400008