On angular measures in Minkowski planes
Following ideas of Brass and Düvelmeyer, the author introduces a translation invariant angular measure for normed planes that has the property that if two James-orthogonal vectors form an angle of measure \({\pi\over 2}\), then the plane is Euclidean. This implication does not hold for Birkhoff orthogonality; it yields a more general class of norms whose unit circles suitably contain arcs which are pieces of Radon curves.
scientific article; zbMATH DE number 5955039