Example of a Spine

Below you find a presentation by boundary curves of a certain special spine of the following Seifert manifold: (S^2; (2,1),(3,1),(9,1),(1,-1)). This spine has 9 vertices, hence 10 cells and 18 edges.

1: 1 6 12 -13 16 -17 -11 -7 -3
2: 2 5 10 -11 15 -18 -13 -8 -4
3: 1 5 -6 -2
4: 1 -2 3 -4
5: 5 12 -14 -10 -6
6: 3 8 -9 -7 -4
7: 11 14 18 -16 -9
8: 13 -14 17 -15 9
9: 10 17 -18 -12
10: 7 15 -16 -8
Please refer here for an explanation of this presentation.