\begin{graph}
   rankdir=LR
   node [shape=plaintext]
   $v_1$(2)
   $v_1$ -> $v_2$ [label=$\sqrt{2}+\frac{1}{x+5}$(5)]
   $v_2$ -> $v_3$ [label=$S \subseteq \{1,2,3\}^4$(4)]
   $v_3$ -> $v_1$ [label=$(f \circ g)^{-1}$(7)]
   A -> B [dir=none]
\end{graph}