\documentclass[a4]{article}

\usepackage{tikz}
\usetikzlibrary{shapes,automata,snakes,backgrounds}
\usepackage[shell]{dot2texi}
\usepackage{amssymb}

\begin{document}

\begin{dot2tex}[options=-tmath]
digraph G{
    d2toptions="--autosize --nominsize";
    a -> b;
    a -> c;
    b -> d;
    d -> a;
}

\end{dot2tex}

\begin{dot2tex}[options=]
 digraph G{
    d2toptions="--autosize --nominsize";
    "c" [
    label = "<f0> C = $\varnothing$ | <f1> meuh" 
    shape = "record"
    ];

    a -> c;
    b -> d;
    d -> a;
}

\end{dot2tex}



\end{document}