I have two questions. There must be an easy way for the diagram that I am trying to draw, but I am totally new to drawing diagrams in tex. Xy-pic package seems too complicated, thus I am trying TikZ-package.
How do I change the arrows in my matrix to simply to
$\Rightarrows$, I solved it by[double], but it does not look nice and the color of arrows are somehow different.How can I add two arrows between two nodes. Simply, I want to write
$A \Rightarrow B$and$B \nLightarrow A$between my two nodes A and B. I could not also solve the bending problem yet.
Here is my code up to now.
\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{matrix,arrows,decorations.pathmorphing}
\begin{document}
\begin{tikzpicture}
\matrix (m) [matrix of math nodes, row sep=3em, column sep=3em, text
height=1.5ex, text depth=0.25ex]
{ & X & & \\
A & B & C & D \\
E & F & G & H \\
& I & & \\};
\path[->] (m-1-2) edge [double] (m-2-3)
edge [double,bend left=90] (m-4-2);
\path[->] (m-2-1) edge [double] (m-2-2)
edge [double] (m-3-1)
edge [double] (m-1-2);
\path[->] (m-2-2) edge [double] (m-2-3)
edge [double] (m-3-2);
\path[->] (m-2-3) edge [double] (m-2-4)
edge [double] (m-3-3);
\path[->] (m-2-4) edge [double] (m-3-4);
\path[->] (m-3-1) edge [double] (m-3-2)
edge [double] (m-4-2);
\path[->] (m-3-2) edge [double](m-3-3);
\path[->] (m-3-3) edge [double] (m-3-4);
\path[->] (m-4-2) edge [double] (m-3-3);
\end{tikzpicture}
\end{document}



