Boreale, Michele and De Nicola, Rocco and Pugliese, Rosario  Asynchronous Observations of Processes.   In:  Foundations of Software Science and Computation Structures (FoSSaCS 1998).   Lecture Notes in Computer Science, 1378 .  Springer, pp. 95-109.  ISBN 3-540-64300-1      (1998)