SIMBAD references

The division of translucent interstellar clouds into σ and ζ types was initiated with the first publications demonstrating variable strength ratios of diffuse interstellar bands (DIBs), the narrower 5797 Å and broader 5780 Å. The paper tests whether this division is zero - one type i.e. whether nothing is between the defined cloud types. We demonstrate that in fact there are many intermediate types of clouds and that their spectra are characterized both by different strength ratios of DIBs and of the features carried by interstellar identified molecules and dust grains.