Before revision:  In addition, the values of \alpha_x and H_x have negligible impacts on H_r, whereas H_s exhibits a dominating impact on H_r. Our results suggest that stock markets are complex adaptive systems and URLanize to a critical state in which the returns are not correlated .
After revision:  In addition, the values of \alpha_x and H_x have negligible impacts on H_r, whereas H_s exhibits a dominating impact on H_r. The predictions of the MMF model on the dependence of H_r upon H_s and H_x are verified by the empirical results obtained from the order flow data of 43 Chinese stocks .