is mentioned by

Thm* For any graph L:V List, i:V, s:Traversal. (j:V. (inr(j) s) (inl(j) s) j-the_graph- > *i) L-- > *i dfl-traversal(the_graph;L;s) dfl-traversal(the_graph;L;[inr(i) / s])	[dfl-traversal-consr]
Thm* For any graph i:V, s:Traversal. (j:V. (inr(j) s) (inl(j) s) j-the_graph- > *i) df-traversal(the_graph;s) df-traversal(the_graph;[inr(i) / s])	[df-traversal-cons2]
Thm* For any graph i,j:V. [i]-- > *j i-the_graph- > *j	[list-connect-singleton]
Thm* For any graph (x,y:V. Dec(x = y)) (x,y:V. x-the_graph- > *y x = y (z:V. z = x & x-the_graph- > z & z-the_graph- > *y))	[connect-iff]
Thm* For any graph x,y:V. x-the_graph- > y x-the_graph- > *y	[edge-connect]
Thm* For any graph x,y:V. x = y x-the_graph- > *y	[connect_weakening]
Thm* For any graph x,y,z:V. x-the_graph- > *y y-the_graph- > *z x-the_graph- > *z	[connect_transitivity]
Def topsortedl(the_graph;L;s) == (i,j:Vertices(the_graph). j = i i-the_graph- > *j i before j s) & (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 s)	[topsortedl]
Def dfl-traversal(the_graph;L;s) == (i:Vertices(the_graph), s1,s2:traversal(the_graph). s = (s1 @ [inr(i)] @ s2) traversal(the_graph) (j:Vertices(the_graph). (inr(j) s2) (inl(j) s2) j-the_graph- > *i)) & (j:Vertices(the_graph). (inr(j) s) L-the_graph- > *j) & (i:Vertices(the_graph), s1,s2:traversal(the_graph). (j:Vertices(the_graph). i-the_graph- > *j non-trivial-loop(the_graph;j)) s = (s1 @ [inl(i)] @ s2) traversal(the_graph) L-the_graph- > *i)	[dfl-traversal]
Def topsorted(the_graph;s) == i,j:Vertices(the_graph). i-the_graph- > *j i = j i before j s	[topsorted]
Def depthfirst-traversal(the_graph;s) == i:Vertices(the_graph), s1,s2:traversal(the_graph). (j:Vertices(the_graph). i-the_graph- > *j non-trivial-loop(the_graph;j)) s = (s1 @ [inl(i)] @ s2) traversal(the_graph) (j:Vertices(the_graph). j = i i-the_graph- > *j (inl(j) s2))	[depthfirst-traversal]
Def df-traversal(G;s) == (i:Vertices(G), s1,s2:traversal(G). s = (s1 @ [inr(i)] @ s2) traversal(G) (j:Vertices(G). (inr(j) s2) (inl(j) s2) j-G- > *i)) & (i:Vertices(G), s1,s2:traversal(G). (j:Vertices(G). i-G- > *j non-trivial-loop(G;j)) s = (s1 @ [inl(i)] @ s2) traversal(G) (j:Vertices(G). i-G- > *j (inr(j) s2)))	[df-traversal]
Def non-trivial-loop(G;i) == j:Vertices(G). j = i & i-G- > *j & j-G- > *i	[non-trivial-loop]
Def L-G- > *x == (yL.y-G- > *x)	[list-connect]

Try larger context: Graphs