Stefano Bistarelli Maurizio Gabbrielli Maria Chiara Meo Francesco Santini Timed Soft Concurrent Constraint Programs. 50-66 2008 COORDINATION http://dx.doi.org/10.1007/978-3-540-68265-3_4 conf/coordination/2008 db/conf/coordination/coordination2008.html#BistarelliGMS08