In an undirected graph, (i,j) means that node i and node j are connected with an undirected edge.
The nodes are numbered from 0 to 12, and the edges are: (12,0) (8,7) (4,1) (11,3) (8,9) (6,5) (9,12) (7,4) (1,3) (4,0) (3,5) (10,3) (4,2) (0,2) (1,0) (0,3).