Linear dilatation and absolute continuity. Koskela, P.; Rogovin, S. — 2005 Annales Academiae Scientiarum Fennicae. Mathematica
Hölder continuity of Sobolev functions and quasiconformal mappings. P. Koskela; F. Reitich — 1993 Mathematische Zeitschrift
Measure density and extendability of Sobolev functions. P. Hajlasz; P. Koskela; H. Tuominen — 2008 Revista Matemática Iberoamericana