E. H. Rühl, F. Manty, H. Konrad, and E. Bleser, “The importance of pathogen-free grapevine propagation material in regards to clonal selection and rootstock breeding in Germany”, Int. j. hortic. sci., vol. 17, no. 3, pp. 11–13., Jun. 2011, doi: 10.31421/IJHS/17/3/952.