Emission of the ¹³CO integrated between 64.3 and 68.6 km s^-1. The green contours are the radio continuum emission from G20. The red crosses are the class I YSO candidates selected following the procedure described in the text. Several YSO candidates appear grouped together in small clusters. One of them (indicated with an arrow) is located right upon the molecular gas, which was probably shocked by the SNR.