Habent Sua Fata Libelli. This proverbial statement of Terentianus Maurus applies in a very particular sense to the present volume of the de Gruyter Studies
in Mathematics.
Werner Fenchel, Professor emeritus at the University of Copenhagen, one of
the pioneers in the theory of convex bodies and in duality theory for convex
functions, well-known also by his contributions to global differential geometry
and other fields of mathematics, died on January 24,1988 quite unexpectedly. At
that time it was clear to both the publisher and the editors that Fenchel's
monograph "Elementary Geometry in Hyperbolic Space" would be accepted for the
de Gruyter Studies. Unfortunately, the publisher's official letter of acceptance
did not reach Werner Fenchel in time.