@string{PRL = "Physical Review Letters"}
@article{runge1984,
  author   = "Erich Runge and Eberhard K. U. Gross",
  title    = "Density-Functional Theory for Time-Dependent Systems",
  journal  = PRL,
  volume   = "52",
  pages    = "997-1000",
  year     = "1984",
  doi      = "10.1103/PhysRevLett.52.997"
}