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

Graph Edges:
1. X13 o-> X9
2. X13 o-o X8
3. X13 o-> X7
4. X5 o-> X12
5. X8 o-> X5
6. X5 o-> X7
7. X11 o-> X5
8. X9 <-> X12
9. X9 o-> X7
10. X10 o-> X12
11. X11 o-> X7
12. X4 o-o X2
