Graph Nodes:
X1;X2;X3;X4;X5;X6;X7;X8;X9;X10;X11;X12;X13

Graph Edges:
1. X1 --> X11
2. X1 --> X6
3. X10 --> X11
4. X10 --> X13
5. X11 --> X13
6. X2 --> X13
7. X2 --> X6
8. X3 --> X11
9. X3 --> X12
10. X3 --> X13
11. X3 --> X6
12. X4 --> X12
13. X4 --> X7
14. X5 --> X9
15. X6 --> X10
16. X6 --> X11
17. X7 --> X9
18. X8 --> X9
19. X9 --> X11
20. X9 --> X13

