Add note about Moggi's work.

thesis.tex

@@ -226,6 +226,10 @@ Explain conventions\dots
 
 \section{Type and effect systems}
 \section{Monadic programming}
+\dhil{Moggi's seminal work applies the notion of monads to effectful
+  programming by modelling effects as monads. More importantly,
+  Moggi's work gives a precise characterisation of what's \emph{not}
+  an effect}
 
 \chapter{Continuations}
 \label{ch:continuations}