Figure 8. Contractible graphs with the number of points n<5

From

Graph Theoretical Models of Closed n-Dimensional Manifolds: Digital Models of a Moebius Strip, a Projective Plane a Klein Bottle and n-Dimensional Spheres

Alexander V. Evako

Applied Mathematics and Physics. 2017, 5(1), 19-27 doi:10.12691/amp-5-1-3