“…Here, X ′ (respectively Y ′ ) denotes an independent copy of X (respectively Y ). An unbiased estimator of squared distance covariance proposed by Székely and Rizzo () is given by for n > 3, where the so‐called ‐centred matrices, , have the additional property that for all i , j and are defined by For p = q = 1, Huo and Székely () have shown that is a U‐statistic, which is degenerate in the case where X and Y are independent. For further details concerning the properties of , we refer to the paper by Huang and Huo ().…”