@article{eCosta:2009yf,
  author = "e Costa, Sandro Silva",
  title = "{Scalar fields, density perturbations and the Chaplygin gas}",
  doi = "10.22323/1.081.0069",
  journal = "PoS",
  year = 2009,
  volume = "ISFTG",
  pages = "069"
}