Marjorie McShane Stephen Beale Sergei Nirenburg The Semantics of Backing Up (Or: What to do with Prepositions and Particles?). 770-775 2006 conf/flairs/2006 FLAIRS Conference db/conf/flairs/flairs2006.html#McShaneBN06 http://www.aaai.org/Library/FLAIRS/2006/flairs06-152.php