Abstract: It is shown that the examples presented 1998 by A. Walz are special cases of a more general class of flexible cross-polytopes in $E^4$. The proof is given by means of 4D descriptive geometry. Further, a parameterization of the one-parameter self-motions of Walz's polytopes is presented.
Keywords: Flexibility, polyhedra, 4D geometry
Classification (MSC2000): 52C25; 51N05, 53A17
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