Kurt Lautenbach Hanno Ridder Liveness in Bounded Petri Nets Which Are Covered by T-Invariants. 358-375 1994 conf/apn/1994 Application and Theory of Petri Nets db/conf/apn/apn1994.html#LautenbachR94 http://dx.doi.org/10.1007/3-540-58152-9_20