Correlation between the sum of the equivalent widths, EW₉₆₀₀, of the two DIBs at 9577 Å and 9633 Å of C with interstellar reddening, E_{B − V}, for 16 sightlines from: 1) Galatzutdinov et al. (2000): 1. HD 37022; 2. HD 80077; 3. HD 167971; 4. HD 168607; 5. HD 169454; 6. HD 183143; 7. HD 186745; 8. HD 190603; 10. HD 194279; 11. HD 195592; 12. HD 198478; 13. HD 206165; 14. HD 224055; 15. BD +40 4220. 2) Cox et al. (2014): 16. HD 161061; 17. 4U 1907+09. The straight line represents the average value of the ratio EW9600 /E_{B − V} = 300 mÅ/mag, excluding the sightlines of #1 HD 37022 (Orion with strong UV) and #2 and #5, HD 80077 and HD 169454 (UV-shielded translucent clouds). The strong bands of C detected by Iglesias-Groth & Esposito (2013) in the direction of the only proto-planetary nebula IRAS 01005+7910, where IR bands of C₆₀ have been detected, are completely out of the correlation. This means that these bands should mostly form in the circumstellar shell. However, determination of the C abundance is precluded there because of the lack of knowledge of the properties and the distribution of circumstellar dust.