Farroni, F., et al. “Homeomorphisms of Finite Inner Distortion: Composition Operators on Zygmund-Sobolev and Lorentz-Sobolev Spaces”. Mathematica Scandinavica, vol. 116, no. 1, Mar. 2015, pp. 34-52, https://doi.org/10.7146/math.scand.a-20450.