diff --git a/REFERENCE.md b/REFERENCE.md
index fcd426c6..52a41b7d 100644
--- a/REFERENCE.md
+++ b/REFERENCE.md
@@ -389,27 +389,35 @@ or using `true` and `false`:
 
     %input(selected=true)
 
-#### HTML5 Custom Data Attributes
+#### Hash Valued Attributes
 
-HTML5 allows for adding [custom non-visible data
-attributes](http://www.whatwg.org/specs/web-apps/current-work/multipage/elements.html#embedding-custom-non-visible-data)
-to elements using attribute names beginning with `data-`. Custom data attributes
-can be used in Haml by using the key `:data` with a Hash value in an attribute
-hash. Each of the key/value pairs in the Hash will be transformed into a custom
-data attribute. For example:
+HTML5 allows for adding
+[custom non-visible data attributes](http://www.whatwg.org/specs/web-apps/current-work/multipage/elements.html#embedding-custom-non-visible-data-with-the-data-*-attributes)
+to elements using attribute names beginning with `data-`. The
+[Accessible Rich Internet Applications](http://www.w3.org/WAI/intro/aria)
+specification makes use of attributes beginning with `aria-`. There are also
+frameworks that use non-standard attributes with a common prefix.
 
-    %a{:href=>"/posts", :data => {:author_id => 123}} Posts By Author
+Haml can help generate collections of attributes that share a prefix like
+these. Any entry in an attribute hash that has a Hash as its value is expanded
+into a series of attributes, one for each key/value pair in the hash, with the
+attribute name formed by joining the “parent” key name to the key name with a
+hyphen.
+
+For example:
+
+    %a{:href=>"/posts", :data => {:author_id => 123, :category => 7}} Posts By Author
 
 will render as:
 
-    <a data-author-id='123' href='/posts'>Posts By Author</a>
+    <a data-author-id='123' data-category='7' href='/posts'>Posts By Author</a>
 
 Notice that the underscore in `author_id` was replaced by a hyphen. If you wish
 to suppress this behavior, you can set Haml's
 {Haml::Options#hyphenate_data_attrs `:hyphenate_data_attrs` option} to `false`,
 and the output will be rendered as:
 
-    <a data-author_id='123' href='/posts'>Posts By Author</a>
+    <a data-author_id='123' data-category='7' href='/posts'>Posts By Author</a>
 
 ### Class and ID: `.` and `#`