Right panel: same diagram as Fig. 3, but with variable classifications from OGLE. Different types of variables are shown as different symbols. An overlapping of OSARGs, SRVs, and Miras can be seen in the lower half of the zoomed-out region. Left panel: same zoomed-out region as Fig. 3, where 24 C-OSARGs, 7 O-SRVs, and 3 O-Miras are optical spectroscopic RSGs (open diamonds). More interestingly, two O-Miras at the upper right are classified as both optical and MIR spectroscopic RSGs (open squares).