Spectra of CH₃CN(5_K-4_K) for the sources for which at least one transition has been detected. The red line is the synthetic spectrum obtained by the best fit within MADCUBA. For G31.41+0.31, the synthetic spectrum is not reported since the fit does not converge. V_LSR of sources G014.99-0.67 and 18445-0222M3 during observations mildly differ from the correct value. V_LSR has been corrected after observations, and given in Table 3.