Regular correlation coefficients of all APO DIBs with λ5849 vs. λ5797 (excluding the sight lines of HD 175156 and HD 148579). Reference C₂, candidate C₂, and C₂-related DIBs span a sequence distinct from the sequence spanned by the 47 ζ, ζσ, and σ main DIBs of Fan et al. (2022), and 106 other DIBs (orange dots, Table D.1) that are strongly correlated with these main DIBs (Appendix D.1). Other APO DIBs are plotted as small grey squares.