Added example with a ref link defn where the reference is never used.

Closes #454.

1 files changed, 11 insertions, 0 deletions

diff --git a/spec.txt b/spec.txt
index 958ca64..c7dce2f 100644
--- a/spec.txt
+++ b/spec.txt
@@ -3131,6 +3131,17 @@ are defined:
 ````````````````````````````````
 
 
+Whether something is a [link reference definition] is
+independent of whether the link reference it defines is
+used in the document.  Thus, for example, the following
+document contains just a link reference definition, and
+no visible content:
+
+```````````````````````````````` example
+[foo]: /url
+.
+````````````````````````````````
+
 
 ## Paragraphs