The SCS values used for the calculations are taken from [1,2]. Both papers contain a much finer division of functional groups, e.g. different SCS values are given for conjugated and non-conjugated compounds. However, an exhaustive list would become unmanageable so only a subset is used here. In most cases the loss of accuracy is not great.
Since values for the 1H increments of isonitriles, azides, sulfoxides and sulfones were not given in  they were estimated using published NMR data.
Literature "Estimation of the Chemical Shifts of Aromatic Protons Using Additive Increments"
Beeby J, Sternhell S, Hoffmann-Ostenhof T, Pretsch E, Simon W Anal. Chem. 45 (1973) 1571-1573
 "Parameter set for the prediction of the 13C-NMR chemical shifts of sp2- and sp-hybridized carbon atoms in organic compounds"
Pretsch E, Fürst A, Robien W Anal. Chim. Acta 248 (1991) 415-428