diff --git a/doc/quickbook/concepts.qbk b/doc/quickbook/concepts.qbk
index 4b53ed2..8f53574 100644
--- a/doc/quickbook/concepts.qbk
+++ b/doc/quickbook/concepts.qbk
@@ -175,6 +175,11 @@ semantics.
     [convertible to `bool`]
     [`!(a == b)`]
   ]
+  [
+    [`iterator_traits<X>::difference_type`]
+    [A signed integral type representing the distance between iterators]
+    []
+  ]
   [
     [`iterator_traversal<X>::type`]
     [Convertible to`single_pass_traversal_tag`]
@@ -207,11 +212,6 @@ valid and respect the stated semantics.
     [`X&`]
     [`r == s` and `r` is dereferenceable implies `++r == ++s.`]
   ]
-  [
-    [`iterator_traits<X>::difference_type`]
-    [A signed integral type representing the distance between iterators]
-    []
-  ]
   [
     [`iterator_traversal<X>::type`]
     [Convertible to `forward_traversal_tag`]