diff --git a/xep.ent b/xep.ent
index db90c8cd..8804f56b 100644
--- a/xep.ent
+++ b/xep.ent
@@ -364,6 +364,7 @@
 <!ENTITY rfc2326 "<span class='ref'><link url='http://tools.ietf.org/html/rfc2326'>RFC 2326</link></span> <note>RFC 2326: Real Time Streaming Protocol (RTSP) &lt;<link url='http://tools.ietf.org/html/rfc2326'>http://tools.ietf.org/html/rfc2326</link>&gt;.</note>" >
 <!ENTITY rfc2327 "<span class='ref'><link url='http://tools.ietf.org/html/rfc2327'>RFC 2327</link></span> <note>RFC 2327: SDP: Session Description Protocol &lt;<link url='http://tools.ietf.org/html/rfc2327'>http://tools.ietf.org/html/rfc2327</link>&gt;.</note>" >
 <!ENTITY rfc2368 "<span class='ref'><link url='http://tools.ietf.org/html/rfc2368'>RFC 2368</link></span> <note>RFC 2368: The mailto URL scheme &lt;<link url='http://tools.ietf.org/html/rfc2368'>http://tools.ietf.org/html/rfc2368</link>&gt;.</note>" >
+<!ENTITY rfc2397 "<span class='ref'><link url='http://tools.ietf.org/html/rfc2397'>RFC 2397</link></span> <note>RFC 2397: The data: URL scheme &lt;<link url='http://tools.ietf.org/html/rfc2397'>http://tools.ietf.org/html/rfc2397</link>&gt;.</note>" >
 <!ENTITY rfc2405 "<span class='ref'><link url='http://tools.ietf.org/html/rfc2405'>RFC 2405</link></span> <note>RFC 2405: The ESP DES-CBC Cipher Algorithm With Explicit IV &lt;<link url='http://tools.ietf.org/html/rfc2405'>http://tools.ietf.org/html/rfc2405</link>&gt;.</note>" >
 <!ENTITY rfc2406 "<span class='ref'><link url='http://tools.ietf.org/html/rfc2406'>RFC 2406</link></span> <note>RFC 2406: IP Encapsulating Security Payload (ESP) &lt;<link url='http://tools.ietf.org/html/rfc2406'>http://tools.ietf.org/html/rfc2406</link>&gt;.</note>" >
 <!ENTITY rfc2409 "<span class='ref'><link url='http://tools.ietf.org/html/rfc2409'>RFC 2409</link></span> <note>RFC 2409: The Internet Key Exchange (IKE) &lt;<link url='http://tools.ietf.org/html/rfc2409'>http://tools.ietf.org/html/rfc2409</link>&gt;.</note>" >