Markus Holzer Martin Kutrib Nondeterministic Finite Automata - Recent Results on the Descriptional and Computational Complexity. 563-580 2009 20 Int. J. Found. Comput. Sci. 4 http://dx.doi.org/10.1142/S0129054109006747 db/journals/ijfcs/ijfcs20.html#HolzerK09