@article{JGG_2000_4_2_a5,
     author = {H. Stachel},
     title = {Flexible {Cross-Polytopes} in the {Euclidean} {4-Space}},
     journal = {Journal for geometry and graphics},
     pages = {159--168},
     publisher = {mathdoc},
     volume = {4},
     number = {2},
     year = {2000},
     url = {http://geodesic.mathdoc.fr/item/JGG_2000_4_2_a5/}
}