Giancarlo Tretola Eugenio Zimeo Extending Web Services Semantics to Support Asynchronous Invocations and Continuation 208-215 2007 conf/icws/2007 ICWS http://doi.ieeecomputersociety.org/10.1109/ICWS.2007.89 db/conf/icws/icws2007.html#TretolaZ07