Example of spectral maps obtained by the HARP instrument, visualized in Appendix C. The T_mb maximum value of the central spectrum dictates the scale of the y-axis in each map. a) and b) show the distribution of spectra for J032837.1+311328, a bonafide Stage I source (see Sect. 4.2) with central concentration of emission. c) and d) show the spectral map for a misfit source, J032840.6+311756, with widespread emission in both lines that result in a Stage II classification.