Line widths and velocity-integrated intensities of HCN and HCO⁺. They follow strong linear relationships, which indicate that HCN and HCO⁺ couple well and there are tight chemical connections. The 14 protostellar cores are plotted with red stars, the seven prestellar cores are plotted with green boxes, and the eight observation positions are reference positions that are offset from the cores. They are plotted with blue inverted triangles.