Foundation item: the National Natural Science Foundation of China (No. 10371079).Acknowledgements The authors would like to thank the referees for their valuable comments and suggestions.
In[6],it is proved that Erceg's pseudo-metric and pointwise pseudo-metric presented by Shi are equivalent.In this paper,it is proved that Theorem 1 in[6]is wrong.Further it is proved that Erceg's pseudo-metric and poi...