  Recent advance in calculations of energy levels of the 1s2$l$2$l^{\prime}$
core-excited states for ions along the Li isoelectronic sequence from carbon to
uranium suggested that theoretical predictions for the 1s2$l$2$l^{\prime}$
transitions are significantly more precise than most of the experimental
results available today and can thus be used for calibrating measured X-ray
spectra. This suggestion is verified in the present work by comparison with
benchmark experimental results. We present a critical compilation of all
available experimental data on the energy levels of the 1s2$l$2$l^{\prime}$
core-excited states of Li-like ions. The compiled experimental data include
uncertainty estimates, which allowed proper weighted averaging and comparison
with theoretical calculations. This comparison confirmed the supremacy of the
most advanced theoretical calculations of the 1s2$l$2$l^{\prime}$ levels over
the best experimental results available today.
