Zur Einzigkeit der Bricardschen Oktaeder

In 1896 R. BRICARD gave a complete description of all flexible octahedra; a different approach is due to R. CONNELLY (1978). In this paper a new proof is given using methods of classical projective geometry. The proof is based on the observation that by a converse of the theorem of IVORY each pair of incongruent octahedra with the same edge lengths is connected with a certain pair of confocal guadrics.