Average spectra obtained from regions of about 5′′ in radius towards each source with the aim of identifying CN lines. The spectra are presented in rest frequency. We only show the frequency range in which transitions of CN appear. The vertical lines indicate such transitions: N = 2–1 J = 5/2–3/2 F = 7/2–5/2 (A), N = 2–1 J = 5/2–3/2, F = 3/2–3/2 and F = 1/2–1/2, (B) and (C), respectively.