@article{hethcote:1970:eba,
    author = {Hethcote, Herbert W.},
     title = {Error bounds for asymptotic approximations of zeros of
              {H}ankel functions occurring in diffraction problems},
   journal = {J. Mathematical Phys.},
    volume = {11},
      year = {1970},
    number = {8},
     pages = {2501–2504},
   mrclass = {33.25},
  mrnumber = {MR0267160 (42 \#2062)},
mrreviewer = {F. W. J. Olver},
       doi = {10.1063/1.1665417}}