diff --git a/introduction/introduction.tex b/introduction/introduction.tex
index 3c32d6b..e6627dc 100644
--- a/introduction/introduction.tex
+++ b/introduction/introduction.tex
@@ -2,7 +2,7 @@
 
 \section{Introduction}
 
-$$ \int_{0\-}^{\infty}  f(t).e^{-s.t}.dt  \; | \; s \in C$$
+$$ \int_{0\-}^{\infty}  f(t).e^{-s.t}.dt  \; | \; s \in \mathcal{C}$$
 
 This thesis describes the application of, mathematical (formal) techniques to
 the design of safety critical systems.