diff --git a/README.rst b/README.rst
index f0d1034..48544aa 100644
--- a/README.rst
+++ b/README.rst
@@ -137,7 +137,7 @@ Main Functions
 
 ``classify(isbn)``
     Returns a dictionary of **classifiers** for a canonical ISBN. For the meaning of these classifiers see OCLC_.
-    Most of the data in the underlying service are for books in English.
+    Most of the data in the underlying service are for books in English. (**See issue #138**).
 
 ``desc(isbn)``
     Returns a small description of the book.