Graph Nodes:
X1;X2;X3;X6;X7;X8;X9;X11;X12;X13

Graph Edges:
1. X1 o-> X13
2. X1 o-> X6
3. X1 o-> X9
4. X11 <-> X13
5. X13 o-o X6
6. X2 o-o X1
7. X2 o-> X12
8. X3 o-o X1
9. X6 <-> X11
10. X7 o-> X11
11. X7 o-> X12
12. X7 o-o X3
13. X8 o-> X11
14. X8 o-> X12
15. X8 o-o X7
16. X9 <-> X11
17. X9 --> X12

