i,j,k:Vertices(the_graph). k-the_graph- > *j k-the_graph- > *i (k':Vertices(the_graph). k' before k L k'-the_graph- > *i) i before j topsortl(the_obj;L)
15. i,j,k:Vertices(the_graph).
k-the_graph- > *j
k-the_graph- > *i
(k':Vertices(the_graph). k' before k L k'-the_graph- > *i) i before j topsortl(the_obj;L) topsortedl(the_graph;L;topsortl(the_obj;L))