  Since the publication of the book several improvements have been made in the theory, some of which are reflected in the <a href="http://www.cs.utexas.edu/users/psp/notesunity.html">notes on UNITY</a>, Jayadev Misra has written a manuscript for a book that presents the <a href="http://www.cs.utexas.edu/users/psp/newunity.html">New UNITY</a>, this includes the introduction of a new temporal operator <em>co</em> for specifying safety.<p>
