%%%------------------------------------------------------------------------------------------------------------
%%%  树结构的表示
\begin{tikzpicture}
{\small
\begin{scope}[sibling distance=3pt, level distance = 22pt]
\Tree[.S [.NN ] [.VP [.AD ] [.VP [.VV ] [.AS ] ] ] ]
\end{scope}
	
\begin{scope}[xshift=1.25in,yshift=0.25in]
\node [anchor=north west,align=left] (string1) at (0,0) {[S \\\hspace{1em}NN\\\hspace{1em}VP[\\\hspace{2.5em}AD \\\hspace{2.5em}VP[\\\hspace{4em}VV \\\hspace{4em}AS]]]};
\end{scope}
	
\begin{scope}[xshift=2.78in,yshift=-0.80in]
\node [anchor=west,align=left] (string2) at (0,0) {(S NN VP(AD \\ VP(VV AS)))};
\end{scope}
	
\node [anchor=north west] (cap1) at (-1.5em,-1in) {{(a) 树状表示}};
\node [anchor=west] (cap2) at ([xshift=0.5in]cap1.east) {{(b) 序列表示（缩进）}};
\node [anchor=west] (cap3) at ([xshift=0.3in]cap2.east) {{(c) 序列表示}};
}
\end{tikzpicture}