diff --git a/10.md b/10.md
index 8b617f6..5fff879 100644
--- a/10.md
+++ b/10.md
@@ -44,9 +44,9 @@ Where:
 
  * `<event-id>` is the id of the event being referenced.
  * `<relay-url>` is the URL of a recommended relay associated with the reference.  It is NOT optional.
- * `<marker>` is optional and if present is one of `"reply"` or `"root"`
+ * `<marker>` is optional and if present is one of `"reply"`, `"root"`, or `"mention"`
 
-**The order of marked "e" tags is not relevant.**  Those marked with `"reply"` denote the `<reply-id>`.  Those marked with `"root"` denote the root id of the reply thread.
+**The order of marked "e" tags is not relevant.**  Those marked with `"reply"` denote the `<reply-id>`.  Those marked with `"root"` denote the root id of the reply thread. Those marked `"mention"` denote id of events that are tagged and are not the `"reply"` nor `"root"`.
 
 A direct reply to the root of a thread should have a single marked "e" tag of type "root".