NMR shieldings from density functional perturbation theory: GIPAW versus   all-electron calculations
  We present a benchmark of the density functional linear response calculation of NMR shieldings within the Gauge-Including Projector-Augmented-Wave method against all-electron Augmented-Plane-Wave$+$local-orbital and uncontracted Gaussian basis set results for NMR shieldings in molecular and solid state systems. In general, excellent agreement between the aforementioned methods is obtained. Scalar relativistic effects are shown to be quite large for nuclei in molecules in the deshielded limit. The small component makes up a substantial part of the relativistic corrections. 
G. A. de Wijs, R. Laskowski, P. Blaha, R. W. A. Havenith, G. Kresse,   M. Marsman
cond-mat.mtrl-sci