(left) Contours of Δχ² = 2.3 and Δχ² = 6.17 in the Ω_m0 × c₂ plane arising from SNe Ia Union2.1 sample (Suzuki et al. 2012) (orange) and current H(z) data (Stern et al. 2010) (green). Black contours stand for the joint analysis involving these two sets of data. (right) Contours of Δχ² = 6.17 in the Ω_m0 × c₂ plane when 7 measurements of the CMB/BAO ratio and 57 measurements of the gas mass fraction of galaxy clusters are added. We have also indicated the region f_R0 < 0 corresponding to the bounds (11) for the best-fit values shown in Table 1.