Comments on Van der Waals supercritical fluid: Exact formulas for special lines [J. Chem. Phys. 135, 084503 (2011)]

The equations for Widom lines for the supercritical van der Waals fluid were considered in the paper J. Chem. Phys. 135, 084503 (2011). But the equations for the speed of sound and its special Widom line were incorrect. The correct equations are obtained.