Amedeo Cesta Alberto Finzi Simone Fratini Andrea Orlandini Enrico Tronci Flexible Timeline-Based Plan Verification. 49-56 2009 KI http://dx.doi.org/10.1007/978-3-642-04617-9_7 conf/ki/2009 db/conf/ki/ki2009.html#CestaFFOT09