¹³ CO map around SNR G35.6−0.4 is shown, where the CO data is obtained from GRS. The x-axis and y-axis represent the RA and Dec, respectively. Noticeably, only the contours of CloudX2 is shown in Fig. 1, meanwhile the western clouds that lack γ-ray counterparts are neglected in this work. The 1.4 GHz image from VGPS is marked in green contours. The best fitted position of SrcX1 and SrcX2 are marked in red diamonds, red circles represent their position uncertainties (2σ). The X-ray point sources and the nearby pulsars are marked in white crosses and circles, respectively. The H II region G35.6−0.5 and the planetary nebulae PN G35.5−0.4 are marked in cyan boxes.