Comparison of observed (solid black circles) and synthetic spectra (lines) for two stars in the sample in the region of some Zr I lines used in abundance analysis. Top panel: O-rich star 2MASS J20560894+5059071 (Berkeley 53). Dashed blue lines: no-Zr and [Zr/M] = 0.0; red continuous line [Zr/M] = +0.5. Bottom panel: Same as for the carbon star IRAS 19582+2967 (FSR 172). Dashed blue lines: no-Zr and [Zr/M] = 0.0; red continuous line [Zr/M] = +0.6. Note the difference in the observed spectrum in this spectral region between an O-rich and a C-rich star; the former star is dominated by TiO and atomic absorptions, whereas the C-star is dominated by CN lines.