CO 16–15 spectra toward all observed sources. The source velocity is marked with a red dashed line in each panel and the baseline is shown in green. The best-fit Gaussian decomposition is overlaid in red, with individual Gaussian components shown in gray. The velocity scale in the L1448, BHR71, and L1157 spectra is from –100 to +100 km s^-1. Ser-SMM4 is not decomposed into Gaussian functions because it appears entirely triangular.