Metal-Insulator Transition in 2D: Experimental Test of the Two-Parameter   Scaling
  We report a detailed scaling analysis of resistivity \rho(T,n) measured for several high-mobility 2D electron systems in the vicinity of the 2D metal-insulator transition. We analyzed the data using the two parameter scaling approach and general scaling ideas. This enables us to determine the critical electron density, two critical indices, and temperature dependence for the separatrix in the self-consistent manner. In addition, we reconstruct the empirical scaling function describing a two-parameter surface which fits well the \rho(T,n) data. 
D.A. Knyazev, O.E. Omel'yanovskii, V.M. Pudalov, I.S. Burmistrov