Based on observations collected using at the European Southern Observatory, La Silla, Chile, the Onsala Space Observatory, Chalmers Tekniska Högskola, Sweden, the James Clerk Maxwell Telescope, Hawaii and the IRAM 30 m telescope, Pico Veleta, Spain.

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... $[12~\mu{\rm m}]-[25~\mu{\rm m}]$

To convert our zero corrected colours to the originally not corrected ones 1 $.\!\!^{\rm m}$ 56 and 1 $.\!\!^{\rm m}$ 88 has to be subtracted from $[12~\mu{\rm m}]-[25~\mu{\rm m}]$ and $[25~\mu{\rm m}]-[60~\mu{\rm m}]$ , respectively.

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