↑ Pappas, T. "The Impossible Tribar." The Joy of Mathematics. San Carlos, CA: Wide World Publ./Tetra, p. 13, 1989.
↑ Francis, George (1988). A topological picturebook. Springer. ISBN0-387-96426-6. In the chapter on the Penrose tribar, Francis attributes this observation to John Stillwell.
↑ Gardner, Martin (1978). Mathematical Games, August 1978 A Möbius band has a finite thickness, and so it is actually a twisted prism. SCIENTIFIC AMERICAN, A DIVISION OF NATURE AMERICA, INC. Chú thích có tham số trống không rõ: |1= (trợ giúp)
