The 2DSA method by Demeler and colleagues aims to solve the same Eqs. (1), (3), and (4), respectively. This is described by Brookes et al. (2009) , and with less mathematical detail by Demeler et al. (2009) . The Demeler approach deviates in key aspects from the strategies described above. Apparently in order to circumvent perceived computational limitations, a novel multigrid scheme is conceived that would allow a sequence of fits with lowresolution 10 9 10 (S 9 F) grids to approximate the solution of (1) and (3) with high-resolution S ) 10 and F ) 10. For achieving parsimonious results Monte Carlo iterations are applied (Brookes et al. 2009 ). Some of the key ideas will be discussed in the following.