Velocity dispersion analysis of the SEPs (electrons shown in the left and protons shown in the right panel) on 2019 May 6. Wind and ACE electron data are used to determine the electron release time. LND proton, ACE/EPAM LEMS30 and LEMS120 ion data are used to determine the proton release time. The linear fits and the fitted parameters of the VDA analysis with 95% confidence interval are marked in the plots. More details can be found in the text of Section 2.2.