Update MutualRecursion.md

Author: BillyBadBoy

docs/MutualRecursion.md

@@ -52,7 +52,7 @@ These are definitions of `IsEven` and `IsOdd` in terms of `F`, which we can subs
 F = λ f . f (λn.(IsZero n) True (F (λ x y . y) (Pred n))) (λn.(IsZero n) False (F (λ x y . x) (Pred n)))
                                  ^^^^IsOdd^^^                                  ^^^^IsEven^^^
 ````
-Notice that there are no references to `IsEven` or `IsOdd` in this equation. This is a definition of `F` that includes references to `F` in its body - i.e. this is an example of simple recursion.
+Notice that there are no explicit references to `IsEven` or `IsOdd` in this equation. This is a definition of `F` that includes references to `F` in its body - i.e. this is an example of simple recursion.
 
 Now we produce a non-recursive definition of `F` by following the procedure for [simple recursion](./SimpleRecursion.md) - let's call the result `F'`. The final step is to re-use the equations above for `IsEven` and `IsOdd` (but with `F'` instead of the equivalent `F`) :
 ````haskell