@article{hill:1981:asv,
    author = {Hill, G. W.},
     title = {Algorithm 571: Statistics for von {M}ises' and {F}isher's
              distributions of directions: {$I_1(x)/I_0(x)$},
             {$I_{1.5}(x)/I_{0.5}(x)$} and their inverses [S14]},
   journal = {ACM Trans. Math. Software},
  fjournal = {Association for Computing Machinery. Transactions on
              Mathematical Software},
    volume = {7},
      year = {1981},
    number = {2},
     pages = {233–238},
      note = {Single-precision Fortran, minimum accuracy 8S.},
      issn = {0098-3500},
       doi = {10.1145/355945.355953},
     links = {\GAMSmodule{TOMS}{571}{8610}}}