diff --git a/doc/permutation_iterator.html b/doc/permutation_iterator.html
index cf344da..03922c4 100644
--- a/doc/permutation_iterator.html
+++ b/doc/permutation_iterator.html
@@ -131,6 +131,9 @@ as IndexIterator and the same
If IndexIterator models Random Access Traversal Iterator and
ElementIterator models Readable Lvalue Iterator then
permutation_iterator models Random Access Iterator.
+If iterator X is interoperable with iterator Y then
+permutation_iterator<X, I1, V1, C2, R1, D1> is interoperable with
+permutation_iterator<Y, I2, V2, C2, R2, D2>.
diff --git a/doc/permutation_iterator_ref.rst b/doc/permutation_iterator_ref.rst
index 132f154..51a4cdc 100644
--- a/doc/permutation_iterator_ref.rst
+++ b/doc/permutation_iterator_ref.rst
@@ -64,6 +64,10 @@ If ``IndexIterator`` models Random Access Traversal Iterator and
``ElementIterator`` models Readable Lvalue Iterator then
``permutation_iterator`` models Random Access Iterator.
+If iterator ``X`` is interoperable with iterator ``Y`` then
+``permutation_iterator
`` is interoperable with
+``permutation_iterator``.
+
``permutation_iterator`` operations
-----------------------------------