@article{amos:1983:pfs,
    author = {Amos, D. E.},
     title = {Algorithm 610. {A} portable {FORTRAN} subroutine for
              derivatives of the psi function},
   journal = {ACM Trans. Math. Software},
  fjournal = {Association for Computing Machinery. Transactions on
              Mathematical Software},
    volume = {9},
      year = {1983},
    number = {4},
     pages = {494–502},
      note = {Single and double precision, maximum accuracy 18S.},
      issn = {0098-3500},
     coden = {ACMSCU},
   mrclass = {65D20},
  mrnumber = {MR0791979},
       doi = {10.1145/356056.356065},
     links = {\GAMSmodule{TOMS}{610}{8648}},
     zblno = {0519.65013}}