M. Rao. Proceedings of the 15th International Conference on Algorithmic Learning Theory (ALT'04), volume 3244 of LNCS, page 69--82. Springer-Verlag, (2004)
D. Angluin. Proceedings of the 2nd Annual Workshop on Computational Learning Theory (COLT'89), page 134--145. San Francisco, CA, USA, Morgan Kaufmann Publishers Inc., (1989)