fix markup

diff --git a/topics/week5_simply_typed.mdwn b/topics/week5_simply_typed.mdwn
index 1a0425f..fc7bfd2 100644 (file)
--- a/topics/week5_simply_typed.mdwn
+++ b/topics/week5_simply_typed.mdwn
@@ -99,8 +99,8 @@ and so on.
 Given a set of types `T`, we define the set of typed lambda terms <code>&Lambda;_T</code>,
 which is the smallest set such that
 
-*    each type `t` has an infinite set of distinct variables, {x^t}_1,
-     {x^t}_2, {x^t}_3, ...
+*    each type `t` has an infinite set of distinct variables, x<sup>t</sup><sub>1</sub>,
+     x<sup>t</sup><sub>2</sub>, x<sup>t</sup><sub>3</sub>, ...
 
 *    If a term `M` has type &sigma; -> &tau;, and a term `N` has type
      &sigma;, then the application `(M N)` has type &tau;.