BibTeX

@ARTICLE{iumj54031,
    author = "D. Lewis",
     title = "On the Perturbation of a Periodic Solution when the Variational System has Non-Trivial Periodic Solutions",
   journal = "Indiana Univ. Math. J.",
  fjournal = "Indiana University Mathematics Journal",
    volume = 4,
      year = 1955,
     issue = 5,
     pages = "795--815",
      issn = "0022-2518",
     coden = "IUMJAB",
   mrclass = "",
}

amsrefs

\bib{iumj54031}{article}{
     author = {Lewis, D.},
      title = {On the Perturbation of a Periodic Solution when the Variational System has Non-Trivial Periodic Solutions},
    journal = {Indiana Univ. Math. J.},
     volume = {4},
       year = {1955},
     number = {5},
      pages = {795 \ndash 815},
}