Borislav H. Simov Giora Slutzki Steven M. LaValle Clearing a Polygon with Two 1-Searchers. 59-92 2009 19 Int. J. Comput. Geometry Appl. 1 http://dx.doi.org/10.1142/S0218195909002836 db/journals/ijcga/ijcga19.html#SimovSL09