*Definition [#z01ea530]
-Let K be a convex subset of a linear topological space X. We say that K is line-closed if L∩K is a closed subset of L (in its unique linear topology) for every line L in X.

*Reference [#uf7de8fc]
-Rosenthal, Haskell, ''L^1-convexity. Functional analysis'', 156--174, Lecture Notes in Math., 1332, Springer, Berlin, 1988.