De Nicola, Rocco and Gorla, Daniele and Pugliese, Rosario  Basic Observables for a Calculus for Global Computing.   In:  Automata, Languages and Programming (ICALP 2005).   Lecture Notes in Computer Science, 3580 .  Springer, pp. 1226-1238.  ISBN 3-540-27580-0      (2005)