Grünbaum's Skeletal Polyhedra
This Demonstration shows Grünbaum's skeletal polyhedra.[more]
Grünbaum  discovered nine regular skeletal polyhedra whose faces are regular skew polygons. Five of them are obtained from the Platonic solids and four from the Kepler–Poinsot polyhedra. To find a skew face in one of them, trace a path along its edges such that each pair of adjacent edges are sides of a face of the polyhedron but no three consecutive edges are sides of a single face. The polygon constructed is called a Petrie polygon [1, pp. 284–285].[less]
Branko Grünbaum published an influential book, called Convex Polytopes, on the subject in 1967 .
 P. R. Cromwell, Polyhedra, New York: Cambridge University Press, 1997.
 B. Grünbaum, "Regular polyhedra—Old and New," Aequationes Mathematicae, 16(1–2), 1977 pp. 1–20. doi.org/10.1007/BF01836414.
 B. Grünbaum, Convex Polytopes (Graduate Texts in Mathematics), 2nd ed., New York: Springer, 2003.