To cite package ‘wfe’ in publications use:

  Kim I, Imai K (2019). _wfe: Weighted Linear Fixed Effects Regression
  Models for Causal Inference_. R package version 1.9.1,
  <https://github.com/insongkim/wfe>.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {wfe: Weighted Linear Fixed Effects Regression Models for Causal
Inference},
    author = {In Song Kim and Kosuke Imai},
    year = {2019},
    note = {R package version 1.9.1},
    url = {https://github.com/insongkim/wfe},
  }