diff --git a/smack-experimental/src/main/java/org/jivesoftware/smackx/httpfileupload/HttpFileUploadManager.java b/smack-experimental/src/main/java/org/jivesoftware/smackx/httpfileupload/HttpFileUploadManager.java
index da2e6d609..47e2ddd8b 100644
--- a/smack-experimental/src/main/java/org/jivesoftware/smackx/httpfileupload/HttpFileUploadManager.java
+++ b/smack-experimental/src/main/java/org/jivesoftware/smackx/httpfileupload/HttpFileUploadManager.java
@@ -64,7 +64,18 @@ import org.jxmpp.jid.DomainBareJid;
  */
 public final class HttpFileUploadManager extends Manager {
 
+    /**
+     * Namespace of XEP-0363 v0.4 or higher. Constant value {@value #NAMESPACE}.
+     *
+     * @see <a href="https://xmpp.org/extensions/attic/xep-0363-0.4.0.html">XEP-0363 v0.4.0</a>
+     */
     public static final String NAMESPACE = "urn:xmpp:http:upload:0";
+
+    /**
+     * Namespace of XEP-0363 v0.2 or lower. Constant value {@value #NAMESPACE_0_2}.
+     *
+     * @see <a href="https://xmpp.org/extensions/attic/xep-0363-0.2.5.html">XEP-0363 v0.2.5</a>
+     */
     public static final String NAMESPACE_0_2 = "urn:xmpp:http:upload";
 
     private static final Logger LOGGER = Logger.getLogger(HttpFileUploadManager.class.getName());
diff --git a/smack-experimental/src/main/java/org/jivesoftware/smackx/httpfileupload/UploadService.java b/smack-experimental/src/main/java/org/jivesoftware/smackx/httpfileupload/UploadService.java
index ae9f90cbb..baf279cd8 100644
--- a/smack-experimental/src/main/java/org/jivesoftware/smackx/httpfileupload/UploadService.java
+++ b/smack-experimental/src/main/java/org/jivesoftware/smackx/httpfileupload/UploadService.java
@@ -23,7 +23,18 @@ import org.jxmpp.jid.DomainBareJid;
 public class UploadService {
 
     enum Version {
+        /**
+         * Upload service as specified in XEP-0363 v0.2 or lower.
+         *
+         * @see <a href="https://xmpp.org/extensions/attic/xep-0363-0.2.5.html">XEP-0363 v0.2.5</a>
+         */
         v0_2,
+
+        /**
+         * Upload service as specified in XEP-0363 v0.3 or higher.
+         *
+         * @see <a href="https://xmpp.org/extensions/attic/xep-0363-0.4.0.html">XEP-0363 v0.4.0</a>
+         */
         v0_3,
     };