\begin{figure}[H]
  \begin{center}
    \unitlength=4pt
    \begin{picture}(72, 18)(0,-2)
    \gasset{Nw=5,Nh=5,Nmr=2.5,curvedepth=3}
    \thinlines
    \node[Nmarks=i,iangle=180](A0)(0,0){$q_0$}
    \node(A1)(12,0){$q_1$}
    \node(A2)(36,0){$q_i$}
    \node(A3)(48,0){$q_{j+1}$}
    \node(A4)(60,0){}       
    \node[Nmarks=f,fangle=270](A5)(72,0){$q_r$}
    \node(A6)(44,8){$q_{i+1}$}
    \node(A7)(24,0){}     
    \node(A8)(36,16){}    
    \node(A9)(28,8){}     
    \gasset{curvedepth=0,ELside=r}
    \drawedge(A0,A1){$a_1$}
    \put(16,0){$\ldots$}
    \drawedge(A7,A2){$a_i$}
    \drawedge(A2,A3){$a_{j+1}$}
    \put(52,0){$\ldots$}
    \drawedge(A4,A5){$a_r$}
    \gasset{curvedepth=-2,ELside=l}
    \drawedge(A2,A6){$a_{i+1}$}
    \drawedge(A6,A8){$a_{i+2}$}
    \drawedge(A9,A2){$a_j$}
    \drawedge[AHnb=0,dash={0.2 1.8}0](A8,A9){}    
    \end{picture}
  \end{center}
  \caption{Illustration du lemme de l'étoile.}
\end{figure}