On the Hardness of Determining Small NFA's and of Proving Lower Bounds on Their Sizes.

Juraj Hromkovic Georg Schnitger On the Hardness of Determining Small NFA's and of Proving Lower Bounds on Their Sizes. 34-55 2008 Developments in Language Theory http://dx.doi.org/10.1007/978-3-540-85780-8_3 conf/dlt/2008 db/conf/dlt/dlt2008.html#HromkovicS08