Copyright © 2009 Xiaohong Fu and Songxiao Li. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
We provide a representation of elements of the space for a locally convex space and and determine
its continuous dual for normed space and . In particular, we study the extension and characterization of isometries on space, when is a normed space with an unconditional basis and with a
symmetric norm. In addition, we give a simple proof of the main result
of G. Ding (2002).