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

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

