1. 
   Oak Leaf Cluster
   noun a United States military decoration consisting of bronze or silver oak leaves and acorns awarded to anyone who has won a given medal before
   Found op http://wordnetweb.princeton.edu/perl/webwn?s=Oak%20Leaf%20Cluster
   
   
2. 
   Oak leaf cluster
   An oak leaf cluster is one of the tiny devices attached to certain ribbons and medals of the United States Armed Forces (and those of some other nations) to give a military award extra meaning. ==Criteria== An oak leaf cluster is worn to denote award of a second or subsequent award for which an Arm...
   Found op http://en.wikipedia.org/wiki/Oak_leaf_cluster
   
   
3. 
   Oak-Leaf Cluster
   In the US military services, an oak-leaf cluster is an insignia consisting of oak leaves and acorns awarded to holders of certain decorations to indicate a further award of the same decoration.
   Found op http://www.probertencyclopaedia.com/browse/FO.HTM
   
   

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