Comparison between the spectra of the stars with large C abundance, stars 20002 and 90085, and two sample stars with similar parameters yet very different CN and CH absorptions. Also, the narrow Ca(H+K) absorption lines indicate very low metallicity ([Fe/H] ≃ −2.2 dex). The green hatched regions are the windows from which we measured the CN and CH indices. The strong features at 4380 Å and 4738 Å are C₂ Swan absorptions.