diff --git a/sandbox/index.mdwn b/sandbox/index.mdwn
index d92a0e1a2..231dae9f7 100644
--- a/sandbox/index.mdwn
+++ b/sandbox/index.mdwn
@@ -39,6 +39,7 @@ Related keywords:
 
 - <[[Zthes - The Zthes specifications for thesaurus representation, access and navigation|http://zthes.z3950.org/]]>
 - <http://www.loc.gov/z3950/agency/profiles/>
+- [[SKOS Simple Knowledge Organization System - home page|https://www.w3.org/2004/02/skos/]]
 
 ---