Modeling a distribution of species with different size and shape to the data depends critically on the accuracy of the Lamm equation solutions (2) that predict the sedimentation profiles for all species. For calculating Lamm equation solutions, Demeler and colleagues apply the ASTFEM algorithm that was recently introduced by Cao and Demeler (2005) . In that work, the authors report two criteria for the performance of their ASTFEM algorithm in comparison with the reference (true) solution: (1) the overall rmsd (referred to by Cao and Demeler as ''L 2 error,'' in a nonstandard definition), and (2) the maximum error in the evolution of concentration profiles.