@article{10934,
  author = {John Cox},
  title = {On Second Helium Ionization as a Cause of Pulsational Instability in Stars.},
  year = {1963},
  journal = {The Astrophysical Journal},
  volume = {138},
  pages = {487},
  month = {Jan-11-1963},
  issn = {0004-637X},
  url = {http://articles.adsabs.harvard.edu/full/1963ApJ...138..487C},
  doi = {10.1086/147661},
}