Benedikt Bollig Peter Habermehl Carsten Kern Martin Leucker Angluin-Style Learning of NFA. 1004-1009 2009 IJCAI http://ijcai.org/papers09/Papers/IJCAI09-170.pdf conf/ijcai/2009 db/conf/ijcai/ijcai2009.html#BolligHKL09