Spectra of the ¹³CO (2–1; black histograms) and (3–2; blue histograms) emission and the C¹⁸O (2–1; green histograms) and (3–2; red histograms) emission at nine different positions in the HL Tau region obtained with our single-dish observations. The position at which the spectra were extracted is labeled at the upper right corner in each panel in relative offset with respect to the position of HL Tau. Vertical dashed lines denote the systemic velocity of HL Tau, V_LSR = 7 km s⁻¹.