Graph Nodes:
X1;X2;X3;X6;X7;X8;X9;X10;X11;X13

Graph Edges:
1. X1 o-> X9
2. X10 --> X13
3. X11 --> X13
4. X2 o-o X1
5. X2 o-> X13
6. X2 o-> X8
7. X3 --> X10
8. X3 --> X11
9. X3 --> X13
10. X3 o-> X8
11. X3 o-> X9
12. X6 o-> X11
13. X6 --> X13
14. X6 o-o X3
15. X6 o-> X8
16. X7 o-> X11
17. X7 o-o X2
18. X8 --> X10
19. X8 --> X13
20. X9 <-> X10
21. X9 --> X11

