Figure 4. T is a digital torus. P is a digital projective plane. K is a digital Klein bottle. M is a digital Moebius band. Graphs T, P, K and M are obtained by identifying gray points with equal numbers

From

Graph Theoretical Models of Discrete Spaces with Locally Non-spherical Topology

Alexander V. Evako

Applied Mathematics and Physics. 2017, 5(2), 47-52 doi:10.12691/amp-5-2-3