Insert a few citations.

thesis.tex

@@ -1678,7 +1678,8 @@ the effect signature $E$.
 This typing discipline fits nicely with the effect handlers-style of
 programming. The $\Do$ construct provides a mechanism for injecting an
 operation into the effect signature, whilst the $\Handle$ construct
-provides a way to eliminate an effect operation from the signature.
+provides a way to eliminate an effect operation from the
+signature~\cite{BauerP13,HillerstromL16}.
 %
 If we instantiate $A = \UnitType$, $B = \Bool$, and $E = \Sigma$, then
 we obtain a type-and-effect signature for the handler version of