Probability density (left panel) and CDFs (right panel) of the white dwarf masses based on the fits to the COS spectra using the La Plata (red) and Montreal (blue) M-R for samples common with K09 (top panels, fits using VCS and TB09 Stark profiles shown in green and black, respectively), and G11 (bottom panels, black). The number of common stars and peak masses of the studies obtained from Gaussian fits are reported in the left panels.