Burdak, Z., and W. Grygierzec. “On Dilation and Commuting Liftings of N-Tuples of Commuting Hilbert Space Contractions”. Annales Universitatis Paedagogicae Cracoviensis Studia Mathematica, vol. 19, Apr. 2020, pp. 121-39, https://studmath.uken.krakow.pl/article/view/7928.