Plots of EQW/E(B − V) of Tc 1 with respect to (w.r.t.) HR 6334 (left panel) and HD 204827 w.r.t. HR 6334 (right panel). The EQW/E(B − V) values of HR 6334 scale nicely w.r.t. HD 204827, which suggests that the properties of ISM are similar for DIBs towards the two stars. For Tc 1, most of the DIBs also scale well w.r.t. HR 6334 (and HD 204827) with the exception of the five unusually strong DIBs (those at ~4428, 5780, 6203, 6284, and 8621 Å; see text), which deviate from the linear relation.