The asymptotic radius r({xn}) of {xn} is given byr({xn}) = inf{r(x, {xn}) : x 2 X},and the asymptotic center A ({xn}) of {xn} is the setA({xn}) = {x 2 X : r(x, {xn}) = r({xn})}A sequence {xn} in X is said to -converge to x 2 X if x is the unique asymptoticcenter of {un} for every subsequence {un} of {xn}. In this case we write limn xn = xand call x the -limit of {xn}, see [19]