BibTeX

@ARTICLE{iumj54036,
    author = "L. Flatto and Norman Levinson",
     title = "Periodic Solutions of Singularly Perturbed Systems",
   journal = "Indiana Univ. Math. J.",
  fjournal = "Indiana University Mathematics Journal",
    volume = 4,
      year = 1955,
     issue = 6,
     pages = "943--950",
      issn = "0022-2518",
     coden = "IUMJAB",
   mrclass = "",
}

amsrefs

\bib{iumj54036}{article}{
     author = {Flatto, L.},
     author = {Levinson, Norman},
      title = {Periodic Solutions of Singularly Perturbed Systems},
    journal = {Indiana Univ. Math. J.},
     volume = {4},
       year = {1955},
     number = {6},
      pages = {943 \ndash 950},
}