Top: classification [c₁] vs. [m₁] diagram for the stars earlier than A0 spectral type with available uvbyβ photometry. Different datasets are marked with different symbols, as indicated on the panel, using the WEBDA source identifications listed in Table 6. The solid line on this diagram represents the main sequence (Crawford 1975, 1978). Middle: comparisons of the average B − V to b − y from the individual sources. Bottom: similar comparisons for the U − B and u − b quantities. Linear fits corresponding to the different datasets are shown on the last two panels.