Let $(E,t)$ be a Hausdorff locally convex space. Either $(E,\sigma (E,E'))$ or \newline $(E',\sigma (E',E))$ is a $DF$-space iff $E$ is of finite dimension (THEOREM). This is the most general solution of the problem studied by Iyahen [2] and Radenovič [3].
@article{118468, author = {Dorota Krassowska and Wieslaw Sliwa}, title = {When $(E,\sigma (E,E'))$ is a $DF$-space?}, journal = {Commentationes Mathematicae Universitatis Carolinae}, volume = {33}, year = {1992}, pages = {43-44}, zbl = {0782.46006}, mrnumber = {1173744}, language = {en}, url = {http://dml.mathdoc.fr/item/118468} }
Krassowska, Dorota; Śliwa, Wiesƚaw. When $(E,\sigma (E,E'))$ is a $DF$-space?. Commentationes Mathematicae Universitatis Carolinae, Tome 33 (1992) pp. 43-44. http://gdmltest.u-ga.fr/item/118468/
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