
\begin{tikzpicture}
  \tikzset{
    ->, % makes the edges directed
    >=Stealth, % makes the arrow heads bold
    node distance=5cm, % specifies the minimum distance between two nodes. Change if necessary.
    every state/.style={thick, fill=white}, % sets the properties for each ’state’ node
    initial text=$ $, % sets the text that appears on the start arrow
  }

  \node[state] (s0) {$s_0$};
  \node[state, right of=s0] (s2) {$s_2$};
  \node[state, below of=s0] (s3) {$s_3$};
  \node[state, right of=s3] (s1) {$s_1$};

  \draw (s0) edge[loop above, above] node{a,0} (s0)
        (s0) edge[right] node{b,1} (s3)
        (s0) edge[above] node{c,1} (s2)
        (s1) edge[below, loop below] node{(a,0), (b,0)} (s1)
        (s1) edge[below] node{c,1} (s3)
        (s2) edge[right] node{(a,1), (b,1)} (s1)
        (s2) edge[below right, bend left] node{c,0} (s3)
        (s3) edge[above left, bend left] node{a,1} (s2)
        (s3) edge[below, loop below] node{b,0} (s3)
        (s3) edge[left, bend left] node{c,1} (s0);
\end{tikzpicture}