(i.e., sin $b$ ) for all the UGSs analyzed in comparison with those 156 associated by our method. At high Galactic latitude, the method seems to be less efficient given the ratio between the number of UGSs analyzed and those associated. This could be due to the non uniform exposure of the archival [[*WISE*]{}]{} observations in the [[*WISE*]{}]{} Preliminary Data Release[^5], and will be re-analyzed once the whole [[*WISE*]{}]{} archive will be available. In addition, we note that our association method could be more efficient at low Galactic latitudes where the blazar catalogs, as the ROMA-BZCAT, are less complete [@massaro09].

We also remark that within the 313 regions of comparison chosen for the UGSs there are 55195 [[*WISE*]{}]{} sources, but only 49 of class A, 213 of class B and 129 of class C, all of them detected in all four [[*WISE*]{}]{} bands and with a signal to noise ratio higher than seven in at least one band, as the blazars in the 2FB sample. The distributions of the $s_b$ and $s_q$ parameters for all the 55195 [[*WISE*]{}]{} sources within the 313 ROCs are shown in Figure \[fig:histogram\]. A blind search of all the possible $\gamma$-ray blazar candidates in the 