Angelo Montanari Adriano Peron Alberto Policriti Theories of omega-Layered Metric Temporal Structures: Expressiveness and Decidability. 79-102 1999 7 Logic Journal of the IGPL 1 http://www3.oup.co.uk/igpl/Volume_07/Issue_01/#montanari db/journals/igpl/igpl7.html#MontanariPP99