On invariant Mobius measure and Gauss-Kuzmin face distribution
  There exists and is unique up to multiplication by a constant function a form of the highest dimension on the manifold of n-dimensional continued fractions in the sense of Klein, such that the form is invariant under the natural action of the group of projective transformations PGL(n+1). A measure corresponding to the integral of such form is called a Mobius measure. In the present paper we deduce an explicit formulae to calculate invariant forms in special coordinates. These formulae allow to give answers to some statistical questions of theory of multidimensional continued fractions. As an example, we show in this work the results of approximate calculations of frequencies for certain two-dimensional faces of two-dimensional continued fractions. 
Oleg Karpenkov