Huculak, Ganna. 2019. “Dependence of Milk Productivity Holstein Cows on the Duration of Lactation Period and organism’s Physiological Activity”. Bulletin of Sumy National Agrarian University. The Series: Livestock, no. 1-2(36-37) (July), 54-57. https://doi.org/10.32845/bsnau.lvst.2019.1-2.8.