Ramesh Hariharan Telikepalli Kavitha Kurt Mehlhorn Faster Algorithms for Minimum Cycle Basis in Directed Graphs. 1430-1447 2008 38 SIAM J. Comput. 4 http://dx.doi.org/10.1137/060670730 db/journals/siamcomp/siamcomp38.html#HariharanKM08