diff --git a/htdocs/manual_correlations.dtd b/htdocs/manual_correlations.dtd
index 498afdd..f7243e6 100644
--- a/htdocs/manual_correlations.dtd
+++ b/htdocs/manual_correlations.dtd
@@ -3,6 +3,8 @@
 <!DOCTYPE correlations[
 	<!ELEMENT correlations 	(correlation)*>
 	<!ELEMENT correlation 	(from, to)>
+	<!ELEMENT from EMPTY>
+	<!ELEMENT to EMPTY>
 
 	<!ATTLIST from
 		sid 	CDATA 		#REQUIRED
diff --git a/htdocs/neural_clusters.dtd b/htdocs/neural_clusters.dtd
index 74043aa..a1a8e41 100644
--- a/htdocs/neural_clusters.dtd
+++ b/htdocs/neural_clusters.dtd
@@ -2,6 +2,7 @@
 
 <!DOCTYPE clusters[
 	<!ELEMENT cluster (alert)*>
+	<!ELEMENT alert EMPTY>
 	<!ATTLIST cluster id CDATA #REQUIRED>
 	<!ATTLIST alert
 		desc CDATA
diff --git a/neural_cluster.c b/neural_cluster.c
index 0d6024f..81f2330 100644
--- a/neural_cluster.c
+++ b/neural_cluster.c
@@ -64,7 +64,9 @@ __AI_neural_clusters_to_xml ( kmeans_t *km, AI_alerts_per_neuron *alerts_per_neu
 	}
 
 	fprintf ( fp, "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n"
-		"<?xml-stylesheet href=\"default.xsl\" type=\"text/xsl\"?>\n\n"
+		"<?xml-stylesheet href=\"default.xsl\" type=\"text/xsl\"?>\n"
+		"<!DOCTYPE neural-clusters PUBLIC \"-//blacklight//DTD NEURAL CLUSTERS//EN\" "
+		"\"http://0x00.ath.cx/neural_clusters.dtd\">\n\n"
 		"<clusters>\n" );
 
 	for ( i=0; i < km->k; i++ )