Beitr\"age zur Algebra und Geometrie
Contributions to Algebra and Geometry
Volume 36 (1995), No. 2

F. J. Craveiro de Carvalho:
An  Equichordal  Characterization of Round Spheres

 Abstract
Characterizations of round spheres are plentiful. The aim of this note
is to present one based on the notions of horizon and equichordality.
This kind of characterization complements research on the relations
between the shape of a body and the shapes of
 its shadow  boundaries (see the paper of Kinczes and Kurusa
[Beitr\"age zur Algebra und Geometrie, 36 (1995) 25- 35]).

MSC 1991: 53C40, 53A07