($\sim$ 13.0%) not recognized low-energy counterparts, for a total of 197 $\gamma$-ray blazar candidates within the 313 UGSs analyzed.

Finally, it is worth stressing that our association procedure provides also interesting information on the sources that do not have a $\gamma$-ray blazar candidates in the SR. The absence of $\gamma$-ray blazar candidates selected according to our association procedure could direct to better use the follow-up resources for identifying other $\gamma$-ray source candidates. For example in the case of the unidentified $\gamma$-ray source: 2FGL J1446.8$-$4701 within the 1604 [[*WISE*]{}]{} sources that lie in its SR, we did not find any $\gamma$-ray blazar candidates. This source has been recently identified with the pulsar PSR 1446-4701 (see Public List of LAT-Detected Gamma-Ray Pulsars) [^6].

Comparison with other methods {#sec:comparison}
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We note that among the 313 UGSs analyzed, there are 70 sources that were also unidentified according to the investigation performed in the first Fermi $\gamma$-ray catalog (1FGL), and 48 of them have been associated with a $\gamma$-ray blazar candidates in our analysis. In particular, a recent analysis of the 1FGL unidentified $\gamma$-ray sources has been carried out using two different statistical approaches: the Classification Tree and the Logistic regression analyses [see @ackermann11b 