1. P. Hajłasz, “Sobolev spaces on an arbitrary metric space,” Potential Anal.,5, No. 4, 403–415 (1996).
2. P. Hajłasz and J. Kinnunen, “Hölder quasicontinuity of Sobolev functions” (to appear).
3. Lecture Notes in Math.;J. O. Strömberg,1989
4. E. M. Stein, Singular Integrals and Differentiability Properties of Functions [Russian translation], Mir, Moscow (1973).
5. P. Hajłasz and O. Martio, “Traces of Sobolev functions on fractal type sets and characterization of extension domains” (to appear).