...Å

This expression applies to the quasars' rest-frame. Due to the similar way the times and the wavelengths are affected by the red shift, for the observer's frame $\tau$ reduces by a factor of (1+z)^1/3, which is only a few percent for this sample, and is much less than the expected errors.

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... index

Data are taken from Giveon et al. (1999) and Kaspi et al. (2005).

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... shift

Data are taken from Bachev et al. (2004) and Sulentic et al. (2007).

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