On Vaisala inequality for angular dilatation of mappings and some   applications
  We study some type of mappings with finite distortion $f:D\rightarrow D^{\prime},$ $D, D^{\prime}\subset{\Bbb R}^n,$ $n\ge 2,$ which admit branch points. It is proved some inequality playing essential role at investigation of some problems of plane and space mappings. As application, it is investigated a problem of removable singularities for open discrete mappings with finite length distortion. 
Evgeny Sevostyanov and Ruslan Salimov
math.CV