Der Satz von v. Staudt-Schleiermacher in Minkowski-Ebenen

Let be a Minkowski-(incidence-)plane and let be the group of free projectivities of , i. e. the subgroup generated by pairs of proper perspectivities with identical centers. Our theorem then asserts that is miquelian if satisfies condition (P ₅), i. e. every free projectivity with 5 fixed points is the identity. But first a lemma is shown, which holds in Möbius- and Laguerre-(incidence-)planes too: if fulfills (P ₅), then every affine derivation of is pappian.