BibTeX

@ARTICLE{iumj56040,
    author = "R. Duffin and A. Schild",
     title = "On the Change of Natural Frequencies Induced by Small Constraints",
   journal = "Indiana Univ. Math. J.",
  fjournal = "Indiana University Mathematics Journal",
    volume = 6,
      year = 1957,
     issue = 4,
     pages = "731--758",
      issn = "0022-2518",
     coden = "IUMJAB",
   mrclass = "",
}

amsrefs

\bib{iumj56040}{article}{
     author = {Duffin, R.},
     author = {Schild, A.},
      title = {On the Change of Natural Frequencies Induced by Small Constraints},
    journal = {Indiana Univ. Math. J.},
     volume = {6},
       year = {1957},
     number = {4},
      pages = {731 \ndash 758},
}