--- a/notes/tex/preamble.tex	Mon Jan 20 23:32:58 2014 +0100
+++ b/notes/tex/preamble.tex	Tue Jan 28 00:42:39 2014 +0100
@@ -71,3 +71,7 @@
 \tikzstyle{every state} = [pretty]
 \tikzstyle{automaton} = [shorten >=1pt, node distance = 3cm, auto, bend angle=20, initial text=]
 \tikzstyle{small} = [every node/.style={scale=0.5}, baseline=(current bounding box.north), font=\LARGE]
+
+\pgfdeclarelayer{background}
+\pgfdeclarelayer{foreground}
+\pgfsetlayers{background,main,foreground}