Thm* For any graph
the_obj:GraphObject(the_graph). paren(V;depthfirst(the_obj)) & no_repeats(V+V;depthfirst(the_obj)) & df-traversal(the_graph;depthfirst(the_obj)) & depthfirst-traversal(the_graph;depthfirst(the_obj)) & ( i:V. (inr(i) depthfirst(the_obj)) & (inl(i) depthfirst(the_obj))) | [depthfirst-properties] |