Natalya Gribovskaya Irina Virbitskaite A Categorical Observation of Timed Testing Equivalence. 35-46 2007 conf/pact/2007 PaCT http://dx.doi.org/10.1007/978-3-540-73940-1_4 db/conf/pact/pact2007.html#GribovskayaV07