digraph G {
       a_1 [texlbl="$\frac{\gamma}{2x^2+y^3}$"];
       a_1 -> a_2 -> a_3 -> a_1
       node [texmode="math"];
       a_1 -> b_1 -> b_2 -> a_3;
       b_1 [label="\\frac{\\gamma}{x^2}"];
       node [texmode="verbatim"]
       b_4 [label="\\beta"]
       a_3 -> b_4 -> a_1;
}