Linearization of the inverse conductivity problem
  A positive function (conductivity) on the edges of a graph induces the Dirichlet-to- Neumann map between boundary values of harmonic functions. The inverse conductivity problem is to find the conductivity from the Dirichlet-to-Neumann map. We will show that the map from logarithm of conductivity to the certain logarithms of the determinants of the submatrices of the Dirichlet-to-Neumann map is linear(!) and so the solution of the inverse problem is reduced to solution of the system of linear equations that arise from disjoint paths in the graph. We will make a calculation for a simple tensor product lattice graph and conjecture that it generalizes to planar and three dimensional graphs and also to the continuous case. Depending on the graph the algorithm resembles or not the layer-stripping. 
David V. Ingerman