To cite CausalImpact in publications use:

Brodersen et al., 2015, Annals of Applied Statistics. Inferring causal impact using Bayesian structural time-series models. https://research.google/pubs/pub41854/

Corresponding BibTeX entry:

  @Article{,
    title = {Inferring causal impact using {B}ayesian structural
      time-series models},
    author = {Kay H. Brodersen and Fabian Gallusser and Jim Koehler and
      Nicolas Remy and Steven L. Scott},
    journal = {Annals of Applied Statistics},
    year = {2014},
    volume = {9},
    pages = {247--274},
    url =
      {https://research.google/pubs/inferring-causal-impact-using-bayesian-structural-time-series-models/},
  }