diff --git a/noninvopamp/noninvopamp.tex b/noninvopamp/noninvopamp.tex
index f9d7b83..2394f6f 100644
--- a/noninvopamp/noninvopamp.tex
+++ b/noninvopamp/noninvopamp.tex
@@ -415,6 +415,106 @@ back to their potential causes.
 
 \section{Extracting Fault Trees form the DAG}
 
+
+
+
+%     \node (g1) [event] {No flow to receiver}
+% 	     child{node (g2) {No flow from Component B}   
+%      	child {node (g3) {No flow into Component B}
+% 	     	   child {node (g4) {No flow from Component A1}
+% 	     	      child {node (t1) {No flow from source1}}
+% 	     	      child {node (b2) {Component A1 blocks flow}}
+%           		}
+% 	A simple fault tree
+% % Author: Zhang Long, Mail: zhangloong[at]gmail.com
+% % \def\pgfsysdriver{pgfsys-dvipdfm.def}
+% % \documentclass{minimal}
+% % \usepackage{tikz}
+% % \usetikzlibrary{shapes.gates.logic.US,trees,positioning,arrows}
+% % \begin{document}
+
+
+\begin{figure}
+\begin{tikzpicture}[
+% Gates and symbols style
+    and/.style={and gate US,thick,draw,fill=blue!40,rotate=90,
+		anchor=east,xshift=-1mm},
+    or/.style={or gate US,thick,draw,fill=blue!40,rotate=90,
+		anchor=east,xshift=-1mm},
+    be/.style={circle,thick,draw,fill=white!60,anchor=north,
+		minimum width=0.7cm},
+    tr/.style={buffer gate US,thick,draw,fill=white!60,rotate=90,
+		anchor=east,minimum width=0.8cm},
+% Label style
+    label distance=3mm,
+    every label/.style={blue},
+% Event style
+    event/.style={rectangle,thick,draw,fill=yellow!20,text width=2cm,
+		text centered,font=\sffamily,anchor=north},
+% Children and edges style
+    edge from parent/.style={very thick,draw=black!70},
+    edge from parent path={(\tikzparentnode.south) -- ++(0,-1.05cm)
+			-| (\tikzchildnode.north)},
+    level 1/.style={sibling distance=7cm,level distance=1.4cm,
+			growth parent anchor=south,nodes=event},
+    level 2/.style={sibling distance=7cm},
+    level 3/.style={sibling distance=6cm},
+    level 4/.style={sibling distance=3cm}
+%%  For compatability with PGF CVS add the absolute option:
+%   absolute
+    ]
+%% Draw events and edges
+    \node (g1) [event] {No flow to receiver}
+	     child{node (g2) {No flow from Component B}   
+     	child {node (g3) {No flow into Component B}
+	     	   child {node (g4) {No flow from Component A1}
+	     	      child {node (t1) {No flow from source1}}
+	     	      child {node (b2) {Component A1 blocks flow}}
+          		}
+	     	   child {node (g5) {No flow from Component A2}
+	     	      child {node (t2) {No flow from source2}}
+	     	      child {node (b3) {Component A2 blocks flow}}
+			}
+		   }
+	     	child {node (b1) {Component B blocks flow}}
+		};
+%% Place gates and other symbols
+%% In the CVS version of PGF labels are placed differently than in PGF 2.0
+%% To render them correctly replace '-20' with 'right' and add the 'absolute'
+%% option to the tikzpicture environment. The absolute option makes the 
+%% node labels ignore the rotation of the parent node. 
+   \node [or]	at (g2.south)	[label=-20:G02]	{};
+   \node [and]	at (g3.south)	[label=-20:G03]	{};
+   \node [or]	at (g4.south)	[label=-20:G04]	{};
+   \node [or]	at (g5.south)	[label=-20:G05]	{};
+   \node [be]	at (b1.south)	[label=below:B01]	{};
+   \node [be]	at (b2.south)	[label=below:B02]	{};
+   \node [be]	at (b3.south)	[label=below:B03]	{};
+   \node [tr]	at (t1.south)	[label=below:T01]	{};
+   \node [tr]	at (t2.south)	[label=below:T02]	{};
+%% Draw system flow diagram
+%   \begin{scope}[xshift=-7.5cm,yshift=-5cm,very thick,
+%		node distance=1.6cm,on grid,>=stealth',
+%		block/.style={rectangle,draw,fill=cyan!20},
+%		comp/.style={circle,draw,fill=orange!40}]
+%   \node [block] (re)					{Receiver};
+%   \node [comp]	 (cb)	[above=of re]			{B}  edge [->] (re);
+%   \node [comp]	 (ca1)	[above=of cb,xshift=-0.8cm]	{A1} edge [->] (cb);
+%   \node [comp]	 (ca2)	[right=of ca1]			{A2} edge [->] (cb);
+%   \node [block] (s1)	[above=of ca1]		{Source1} edge [->] (ca1);
+%   \node [block] (s2)	[right=of s1]		{Source2} edge [->] (ca2);
+%   \end{scope}
+\end{tikzpicture}
+\caption{Example FTA for a Gas Supply with two  Shutoff Valves}
+\end{figure}
+\clearpage
+
+
+
+
+
+\clearpage
+
 show an example fault tree, showing the causes and logical (only OR's here)
 
 \section{Extracting FMEA Analysis from the DAG}
@@ -439,3 +539,4 @@ statistical literature is available ~\cite{mil1991}~\cite{fmd91}.
 Software used to edit these diagrams, keeps the model in a directed acyclic graph data structure
 for this purpose.
 
+%\end{document}
\ No newline at end of file
diff --git a/noninvopamp/paper.tex b/noninvopamp/paper.tex
index 2491464..c5565bc 100644
--- a/noninvopamp/paper.tex
+++ b/noninvopamp/paper.tex
@@ -5,6 +5,7 @@
 \usepackage{fancyhdr}
 \usepackage{tikz}
 \usepackage{amsfonts,amsmath,amsthm}
+\usetikzlibrary{shapes.gates.logic.US,trees,positioning,arrows}
 \input{../style}
 \usepackage{ifthen}
 \usepackage{lastpage}
diff --git a/related_papers_books/andrews-fta-tutor.pdf b/related_papers_books/andrews-fta-tutor.pdf
new file mode 100644
index 0000000..99a4952
Binary files /dev/null and b/related_papers_books/andrews-fta-tutor.pdf differ
diff --git a/sw_model/paper.tex b/sw_model/paper.tex
index 57c9947..7de9aad 100644
--- a/sw_model/paper.tex
+++ b/sw_model/paper.tex
@@ -3,7 +3,11 @@
 \usepackage{graphicx}
 \usepackage{fancyhdr}
 \usepackage{tikz}
+
 \usepackage{amsfonts,amsmath}
+\usetikzlibrary{shapes,arrows}
+
+\usepackage{verbatim}
 
 \usepackage{ifthen}
 \newboolean{paper}
diff --git a/sw_model/sw_model.tex b/sw_model/sw_model.tex
index 72da36c..4fc784f 100644
--- a/sw_model/sw_model.tex
+++ b/sw_model/sw_model.tex
@@ -125,6 +125,96 @@ This analysis and symptom collection process is described in detail in the Sympt
 
 
 
+
+%\begin{comment}
+%
+%:Title: Control system principles
+%
+%:Tags: Block diagrams 
+%
+%
+%
+%An example of a control system with a feedback loop. Block diagrams like this
+%
+%are quite time consuming to create by hand. The relative node placement feature
+%
+%makes it a bit easier, but it works best when the nodes have equal widths. 
+%
+%However, the results are quite pleasing and hopefully worth the effort. 
+%
+%You can probably speed up the process by creating custom macros. 
+%
+%\end{comment}
+%
+
+
+
+
+
+
+%
+%\tikzstyle{block} = [draw, fill=blue!20, rectangle, 
+%
+%    minimum height=3em, minimum width=6em]
+%
+%\tikzstyle{sum} = [draw, fill=blue!20, circle, node distance=1cm]
+%
+%\tikzstyle{input} = [coordinate]
+%
+%\tikzstyle{output} = [coordinate]
+%
+%\tikzstyle{pinstyle} = [pin edge={to-,thin,black}]
+%
+%
+%
+%% The block diagram code is probably more verbose than necessary
+%
+%\begin{tikzpicture}[auto, node distance=2cm,>=latex']
+%
+%    % We start by placing the blocks
+%
+%    \node [input, name=input] {};
+%
+%    \node [sum, right of=input] (sum) {};
+%
+%    \node [block, right of=sum] (controller) {Controller};
+%
+%    \node [block, right of=controller, pin={[pinstyle]above:Disturbances},
+%
+%            node distance=3cm] (system) {System};
+%
+%    % We draw an edge between the controller and system block to 
+%
+%    % calculate the coordinate u. We need it to place the measurement block. 
+%
+%    \draw [->] (controller) -- node[name=u] {$u$} (system);
+%
+%    \node [output, right of=system] (output) {};
+%
+%    \node [block, below of=u] (measurements) {Measurements};
+%
+%
+%
+%    % Once the nodes are placed, connecting them is easy. 
+%
+%    \draw [draw,->] (input) -- node {$r$} (sum);
+%
+%    \draw [->] (sum) -- node {$e$} (controller);
+%
+%    \draw [->] (system) -- node [name=y] {$y$}(output);
+%
+%    \draw [->] (y) |- (measurements);
+%
+%    \draw [->] (measurements) -| node[pos=0.99] {$-$} 
+%
+%        node [near end] {$y_m$} (sum);
+%
+%\end{tikzpicture}
+%
+
+
+
+
 \section{ Modern Devices }
 
 From the automobile to the microwave oven, we increasingly rely on