diff --git a/includes/bootstrap.inc b/includes/bootstrap.inc
index 8520733d584a1821be03ea2dea30869ae832a2bb..dd032cb4cd04a9db5f4b79cbead18b0fcc60eb62 100644
--- a/includes/bootstrap.inc
+++ b/includes/bootstrap.inc
@@ -51,6 +51,9 @@
 /**
  * Log message severity -- Emergency: system is unusable.
  *
+ * The WATCHDOG_* constant definitions correspond to the logging severity levels
+ * defined in RFC 3164, section 4.1.1: http://www.faqs.org/rfcs/rfc3164.html
+ *
  * @see watchdog()
  * @see watchdog_severity_levels()
  */
@@ -59,6 +62,9 @@
 /**
  * Log message severity -- Alert: action must be taken immediately.
  *
+ * The WATCHDOG_* constant definitions correspond to the logging severity levels
+ * defined in RFC 3164, section 4.1.1: http://www.faqs.org/rfcs/rfc3164.html
+ *
  * @see watchdog()
  * @see watchdog_severity_levels()
  */
@@ -67,6 +73,9 @@
 /**
  * Log message severity -- Critical: critical conditions.
  *
+ * The WATCHDOG_* constant definitions correspond to the logging severity levels
+ * defined in RFC 3164, section 4.1.1: http://www.faqs.org/rfcs/rfc3164.html
+ *
  * @see watchdog()
  * @see watchdog_severity_levels()
  */
@@ -75,6 +84,9 @@
 /**
  * Log message severity -- Error: error conditions.
  *
+ * The WATCHDOG_* constant definitions correspond to the logging severity levels
+ * defined in RFC 3164, section 4.1.1: http://www.faqs.org/rfcs/rfc3164.html
+ *
  * @see watchdog()
  * @see watchdog_severity_levels()
  */
@@ -83,6 +95,9 @@
 /**
  * Log message severity -- Warning: warning conditions.
  *
+ * The WATCHDOG_* constant definitions correspond to the logging severity levels
+ * defined in RFC 3164, section 4.1.1: http://www.faqs.org/rfcs/rfc3164.html
+ *
  * @see watchdog()
  * @see watchdog_severity_levels()
  */
@@ -91,6 +106,9 @@
 /**
  * Log message severity -- Notice: normal but significant condition.
  *
+ * The WATCHDOG_* constant definitions correspond to the logging severity levels
+ * defined in RFC 3164, section 4.1.1: http://www.faqs.org/rfcs/rfc3164.html
+ *
  * @see watchdog()
  * @see watchdog_severity_levels()
  */
@@ -99,6 +117,9 @@
 /**
  * Log message severity -- Informational: informational messages.
  *
+ * The WATCHDOG_* constant definitions correspond to the logging severity levels
+ * defined in RFC 3164, section 4.1.1: http://www.faqs.org/rfcs/rfc3164.html
+ *
  * @see watchdog()
  * @see watchdog_severity_levels()
  */
@@ -107,6 +128,9 @@
 /**
  * Log message severity -- Debug: debug-level messages.
  *
+ * The WATCHDOG_* constant definitions correspond to the logging severity levels
+ * defined in RFC 3164, section 4.1.1: http://www.faqs.org/rfcs/rfc3164.html
+ *
  * @see watchdog()
  * @see watchdog_severity_levels()
  */