P. T. Nagy, J. Kátai, J. Nyéki, and Z. Szabó, “Effect of frost damage on leaf macronutrient status of eight apple cultivars in integrated apple orchard in Eastern-Hungary”, Int. j. hortic. sci., vol. 14, no. 1-2, pp. 37–40., Feb. 2008, doi: 10.31421/IJHS/14/1-2./779.