Wang also criticized the justifications of the energy–velocity definition and the imposed four-vector covariance in Laue–Møller criterion. Regarding the energy–velocity definition which is given by Poynting vector divided by EM energy density in Laue–Møller criterion, Wang argues "the Poynting vector does not necessarily denote the direction of real power flowing" in a moving medium. Regarding the imposed four-velocity covariance, which was probably prompted by the relativistic velocity addition rule applied to illustrating Fizeau running water experiment, Wang argues that any massive particle has its four-velocity, while the photon (the carrier of EM energy) does not. Since the photon does not have a four-velocity, the Fizeau running water experiment should be taken to be in support of the Minkowski momentum, instead of the experimental evidence of the relativistic four-velocity addition rule.