Quantity diagram (a so-called Venn diagram) of the respective sub-populations of the 33 confirmed quasars. The numbers in each of the symbols represents the objects with the same numbering as in Table 1. The parent sample of quasars consists of 7/33 ~ 21% HAQs. Only quasars 2 and 11 have been selected by one technique alone from KX selection or X-ray detection, respectively. Of the 13 quasars with A_V > 0.1, 6 were selected by the HAQ criteria, 11 were identified by the KX selection, 12 with X-ray detection, 6 had radio detections, 5 were from the photometric selection of SDSS/BOSS, and 4 of the reddened quasars were identified by the MIR selection.