@article{olver:1976:ieb,
    author = {Olver, F. W. J.},
     title = {Improved error bounds for second-order differential equations
              with two turning points},
   journal = {J. Res. Nat. Bur. Standards Sect. B},
    volume = {80B},
      year = {1976},
    number = {4},
     pages = {437–440},
   mrclass = {65L05},
  mrnumber = {MR0448907 (56 \#7212)},
mrreviewer = {Peter Deuflhard},
     zblno = {0357.34009}}