Affinity of angle preserving mappings
It is proved that the preservation of an angle (nonzero and nonstraight) is sufficient for a mapping \(\mathbb{R}^2\to \mathbb{R}^2\) to be a similarity. In terms of circle-preserving mappings a criterion is given for the fact that the mapping of an \(n\)-dimensional space into itself is a similarity.
scientific article; zbMATH DE number 1977046