appendix, instroduction

background.tex

@@ -1,4 +1,4 @@
-\begin{chapter}{Background}
+\begin{chapter}{Background}\label{background_chap}
   \begin{section}{Reaction Systems}
     Reaction Systems are a qualitative model inspired by biochemical processes.
     The behavior is described by reactions, each of them requiring some reactants \(R\) and requiring the absence of inhibitors \(I\) to produce some product elements \(P\). ``Elements'' and ``entities'' will be used interchangeably to refer to elements of these sets.