An improved boundary element-free method (IBEFM) for two-dimensional potential problems
Ren Hong-Ping(任红萍), Cheng Yu-Min(程玉民), and Zhang Wu(张武)
Chin. Phys. B . 2009, (10): 4065 -4073 .  DOI: 10.1088/1674-1056/18/10/002