Upper panel: radio-to-γ-ray SEDs for the 34 objects analyzed in this paper (colored dots). Solid lines represent parabolic fits to the radio-X-ray data. Vertical dotted lines identify the parabola apices, which give an indication of the synchrotron peak position. For the objects without X-ray detection, the peak location should be considered an upper limit. Lower panels: luminosities versus the synchrotron peak frequency. Blue dots, red diamonds, green squares, and pink asterisks refer to radio, infrared, optical, and X-ray bands, respectively. In all panels, upper limits due to the lack of detection in the X-ray band are indicated with arrows.