Introduction. Any finite group of linear transformations on n variables leaves invariant a positive definite Hermitian form, and can therefore be expressed, after a suitable change of variables, as aâ€¦ (More)

Introduction. The purpose of this paper is to survey recent results related to the second part of Hubert's eighteenth problem (see Hilbert [1900]). This problem, which is concerned with tilings ofâ€¦ (More)

A tiling d of the plane or of the 2sphere is said to be homeotoxul if the group H(g), whose elements are the homeomorphisms of the plane or 2sphere which map & onto itself, is transitive on the edgesâ€¦ (More)

In the case n=d = 2, because of Cauchy's surface-area formula [2; p. 208], relation (3) reduces to the trivial statement that the perimeter of a convex polygon is equal to the sum of the lengths ofâ€¦ (More)