diff --git a/index.html b/index.html
index 9811d58..2f156bd 100644
--- a/index.html
+++ b/index.html
@@ -218,7 +218,7 @@
     
     <p id="req-mobile-specific" class=req>The user agent MUST be able to display content specifically targeted at mobile devices.</p>
     
-    <p id="req-responsive" class=req>It MUST be possible for the user agent to download and display different content depending on device or user agent properties such as screen size, pixel density, etc.</p>
+    <p id="req-responsive" class=req>The user agent MUST be able to perform [reactive content negotiation](http://tools.ietf.org/html/draft-ietf-httpbis-p2-semantics-24#section-3.4) specifically targeted at mobile devices. This includes, but is not limited to, discriminating on viewport dimensions, pixel density, and possibly even bandwidth.</p>
     
     <p id="req-rich-fonts" class=req>The user agent MUST support rich typography including using downloadable fonts.</p>