Proper motions of the structures in the A, B, C, D, and E knots of HL Tau jet, corresponding to high a) and low b) radial velocities, are shown by vectors plotted in the images in Hα emission corresponding to −150 km s ^-1 and −50 km s ^-1, respectively. The scale of the vectors is indicated by the arrow at the top of the left panel. Rectangles show the areas used for the difference square method.