Euclidean normalized differential number counts at the LFI frequencies. The red circles with Poisson error bars show the counts of sources with counterparts in our reference 30 GHz sample. In each panel, the solid curves show the total number counts of extragalactic radio sources predicted by the de Zotti et al. (2005) model. Also shown are: the counts estimated at 31 GHz from DASI (grey dashed box; Kovac et al. 2002) and at 33 GHz from the VSA data (grey box; Cleary et al. 2005); the counts from the PACO (grey diamonds; Bonavera et al. 2011) and the WMAP 5-yr surveys (grey squares; Massardi et al. 2009), at the closest frequencies, and the counts estimated by Waldram et al. (2007) (grey dashed line), exploiting multi-frequency follow-up observations of the 15 GHz 9C sources. The vertical dashed magenta line in the upper panel indicates the flux density completeness limit, 1.0Jy, estimated for our primary sample Sect. 2.3.