#+LATEX_HEADER: \usepackage{tikz}

* Tikz Sample
  In figure \ref{fig:tikz_sample} you can see something.
  
  #+srcname: tikz_sample
  #+begin_src latex :exports (if (eq backend 'latex) "none" "results") :file tikz_sample.pdf :headers '("\\usepackage{tikz}")
    \usetikzlibrary{arrows}
    \tikzstyle{int}=[draw, fill=blue!20, minimum size=2em]
    \tikzstyle{init} = [pin edge={to-,thin,black}]
    
    \begin{tikzpicture}[node distance=2.5cm,auto,>=latex']
        \node [int, pin={[init]above:$v_0$}] (a) {$\frac{1}{s}$};
        \node (b) [left of=a,node distance=2cm, coordinate] {a};
        \node [int, pin={[init]above:$p_0$}] (c) [right of=a] {$\frac{1}{s}$};
        \node [coordinate] (end) [right of=c, node distance=2cm]{};
        \path[->] (b) edge node {$a$} (a);
        \path[->] (a) edge node {$v$} (c);
        \draw[->] (c) edge node {$p$} (end) ;
    \end{tikzpicture}
   #+end_src

   #+begin_src latex :noweb yes
     \begin{figure}
       \centering
       <<tikz_sample>>
       \caption[Tikz]{Tikz}\label{fig:tikz_sample}
     \end{figure}
   #+end_src