@article{etna_vol39_pp113-143,
  author  = {Andreas Kleefeld and Tzu-Chu Lin},
  title   = {Boundary element collocation method for solving the exterior Neumann problem for Helmholtz's equation in three dimensions},
  journal = {Electron. Trans. Numer. Anal.},
  volume  = {39},
  year    = {2012},
  pages   = {113--143},
}