ABSTRACT
In 1952 A.W. Ingleton proved that every locally convex space over a spherically complete valued field has the Hahn-Banach extension property. This paper is a survey of the more important results obtained by different authors in the last years about the extension property for locally convex spaces over non-spherically complete fields and for non-locally convex spaces. Also, we include some new contributions of the author on this subject.
