| 1 | 13. x:Vertices(the_graph)+Vertices(the_graph). ((x s2) & (x s)) 14. paren(Vertices(the_graph);s2) 15. no_repeats(Vertices(the_graph)+Vertices(the_graph);s2) 16. (inr(i) s2) 17. j:Vertices(the_graph). (inr(j) s2)  i-the_graph- > *j 18. df-traversal(the_graph;([inl(i)] @ s2 @ [inr(i)]) @ s) 19. i@0:Vertices(the_graph). L1 @ [i]-the_graph- > *i@0  non-trivial-loop(the_graph;i@0) 20. L1@0,L2:Vertices(the_graph) List.
L1 = (L1@0 @ L2)

( s1,s2:traversal(the_graph).
s = (s2 @ s1) traversal(the_graph)
& paren(Vertices(the_graph);s1) & paren(Vertices(the_graph);s2)
& ( j:Vertices(the_graph).
((inl(j) s1)  L1@0-the_graph- > *j)
& ((inl(j) s2)  L2-the_graph- > *j & L1@0-the_graph- > *j))) 21. L1@0: Vertices(the_graph) List 22. L2: Vertices(the_graph) List 23. (L1 @ [i]) = (L1@0 @ L2) 24. e: Vertices(the_graph) List 25. L1 = (L1@0 @ e) 26. L2 = (e @ [i]) 27. s1: traversal(the_graph) 28. s3: traversal(the_graph) 29. s = (s3 @ s1) traversal(the_graph) 30. paren(Vertices(the_graph);s1) 31. paren(Vertices(the_graph);s3) 32. j:Vertices(the_graph).
((inl(j) s1)  L1@0-the_graph- > *j) & ((inl(j) s3)  e-the_graph- > *j & L1@0-the_graph- > *j) 33. j: Vertices(the_graph) 34. (inl(j) s3)  e-the_graph- > *j & L1@0-the_graph- > *j 35. (inl(j) s3)  (e-the_graph- > *j & L1@0-the_graph- > *j) 36. (inl(j) s2) 37. L1@0-the_graph- > *j 38. (inl(j) s1) (inl(j) s3 @ s1) | 1 step |