Robert C. Holte Ariel Felner Jack Newton Ram Meshulam David Furcy Maximizing over multiple pattern databases speeds up heuristic search. 1123-1136 2006 170 Artif. Intell. 16-17 http://dx.doi.org/10.1016/j.artint.2006.09.002 db/journals/ai/ai170.html#HolteFNMF06