NANTEN brightness temperature spectra for ¹²CO(J = 1–0) (black), ¹³CO(J = 1–0) (blue, scaled by a factor of two), and C¹⁸O(J = 1–0) (red, scaled by a factor of five) at selected integrated intensity peaks of the GMC. The numbers in the upper left-hand corners of each panel indicate the Galactic longitude and latitude at which each spectrum was taken.