Observed spectra of the 13 sources with methanol maser emission and the one with methanol absorption. For every source, the top and bottom panels represent D- and B-configuration data, respectively. These spectra were extracted at the peak pixel from the data cubes (see text). The vertical lines show the systemic LSR velocities of the dense molecular gas of the star-forming regions that host the masers, which were taken from the literature (see Table 6).