Before revision:  We also show that our idea can be extended to  the general case of MEB with outliers ({\em i.e.,} without the stability assumption) , and obtain a sub-linear time bi-criteria approximation algorithm.
After revision:  We also show that our idea can be extended to the general case of MEB with outliers ({\em i.e.,} without the stability assumption) and the problem of k-center clustering with outliers. We achieve sub-linear time bi-criteria approximation algorithm.