Separation by hyperplanes in finite-dimensional vector spaces over Archimedean ordered fields.
Separation theorems for sets in product spaces and equivalent assertions
Simple construction of spaces without the Hahn-Banach extension property
An elementary construction for an abundance of vector topologies on a fixed infinite dimensional vector space such that has not the Hahn-Banach extension property but the topological dual separates points of from zero is given.
Some consequences of a kind of Hahn-Banach's theorem
Spectral properties of operators that characterize .