1. Benz, W.: On mappings preserving a single Lorentzr-Minkowski-distance. I In: Proceedings of a conference in Rome, 1981, in memoriam of Beniamino Segre. To appear.
2. Benz, W.: Part II. To appear J. of.Geom.
3. Rado, F.: On the characterization of plane affine isometries. Resultate d. Math. 3 (1980), 70–73.
4. Tallini, G.: On a theorem by W. Benz characterizing plane Lorentz Transformations in Jaernefelt's World. To appear J. of. Geom.