“…4(a) shows a regular directed multigraph G of indegree and outdegree 3 and its cycle covers (C 1 : thin, C 2 : thick, C 3 : dashed). C 1 consists of cycles c 1 : (5, 1, 2, 3, 4, 5) and c 2 : (6,7,8,9,6). We set 4 as the topmost vertex of c 1 since edge (4, 6) of C 2 has vertex 6 of c 2 as its destination.…”