On inflection points of the plane quartic with two nodal and one flexnodal points
On opposite angle points in isotropic triangle geometrics. (Zu den Winkelgegenpunkten der isotropen Dreiecksgeometrie.)
On permutable quadratic inversions in plane with two common singular points
On the Dimensions of Automorphism Groups of Eight-Dimensional Double Loops.
On the dimensions of automorphism groups of four-dimensional double loops.
On the fixed point of a collineation of the real projective plane.
On the geometric relation of twin-points of the triangle. (Zur Verwandtschaft der Zwillingspunkte beim Dreieck.)
On the geometry of symplectic involutions.
On the integral geometry of the linear subspaces in a biplanar space
On the matrices of central linear mappings
We show that a central linear mapping of a projectively embedded Euclidean -space onto a projectively embedded Euclidean -space is decomposable into a central projection followed by a similarity if, and only if, the least singular value of a certain matrix has multiplicity . This matrix is arising, by a simple manipulation, from a matrix describing the given mapping in terms of homogeneous Cartesian coordinates.
On the superadditivity of secant defects
On the theorems of central axonometry.
On the upward motion of a double cone on an inclined plane.
One generalization of quasifield
Opravy k článku Afinity v třírozměrném afinním prostoru
Orientierung in angeordneten affinen Räumen
Orthogonale Erzeugendenpolygone auf einschaligen Hyperboloiden.
Osculatory behavior and second dual varieties of Del Pezzo surfaces.
Ovali ed altre curve nei piani di Galois di caratteristica due