A New Fast-Multipole Accelerated Poisson Solver in Two Dimensions. - J. Frank Ethridge; Leslie Greengard (SIAM J. Sci. Comput., 2001)

A wideband fast multipole method for the Helmholtz equation in three dimensions. - Hongwei Cheng; William Y. Crutchfield; Zydrunas Gimbutas; Leslie Greengard; J. Frank Ethridge; Jingfang Huang; Vladimir Rokhlin; Norman Yarvin; Junsheng Zhao (J. Comput. Phys., 2006)