Lower panel: histogram of the difference Δ E(V − I) between the present study and those of Udalski et al. (1999) shown by a continuous line, and Sandage et al. (2004) shown by a dashed line. Upper panel: heat map representing the difference in reddening divided by reddening uncertainty in each segment, left panel – between the present reddening estimates and those of Udalski et al. (1999); right panel – between the present reddening estimates and those of Sandage et al. (2004). The difference is obtained by subtracting the results of other studies from our estimates.