@article{stenger:1966:ebaa,
    author = {Stenger, Frank},
     title = {Error bounds for asymptotic solutions of differential
              equations. {I}. {T}he distinct eigenvalue case},
   journal = {J. Res. Nat. Bur. Standards Sect. B},
    volume = {70B},
      year = {1966},
     pages = {167–186},
   mrclass = {34.50 (45.00)},
  mrnumber = {MR0219823 (36 \#2901)},
mrreviewer = {F. W. J. Olver},
     zblno = {0233.65048}}