... 35, No. 8, pp. 563­573. i He, C, N, and O Abundances in an Ensemble of Galactic Planetary Nebulae Yu. ... Taking into account the inaccuracies in the corrections for the ionization stages of the elements whose lines are absent in the PNe spectra increases the errors in the He abundance to 0.1 dex and in the C, N, and O abundances to 0.2­0.3 dex. ... To ascertain which PNe belonging to the Galactic disk are similar to bulge objects, we compared the He, C, N, and O abundances in bulge and disk nebulae...