...1,

Present address: Ohio State University, Columbus, Ohio.

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...1,

Present address: Joint Astronomy Centre, Hilo, Hawaii.

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... radiation

For low-excitation lines this may not be entirely correct, but we estimate that the additional error introduced will be no more than 20% for $T_{\rm ex} \sim 10$ K.

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... meanings

As $\int{{T_{\rm R}}}{\rm d}v$ has been approximated by $T_{\rm R}$$\Delta v$ in this formula, a factor of $\sim$1.06, which relates the integrated intensity of a Gaussian profile to the FWHM, has been neglected.

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