To cite package ‘JuliaCall’ in publications use:

  Li C (2019). “JuliaCall: an R package for seamless integration
  between R and Julia.” _The Journal of Open Source Software_, *4*(35),
  1284. doi:10.21105/joss.01284 <https://doi.org/10.21105/joss.01284>.

A BibTeX entry for LaTeX users is

  @Article{JuliaCall,
    author = {Changcheng Li},
    title = {{JuliaCall}: an {R} package for seamless integration between {R} and {Julia}},
    journal = {The Journal of Open Source Software},
    publisher = {The Open Journal},
    year = {2019},
    volume = {4},
    number = {35},
    pages = {1284},
    doi = {10.21105/joss.01284},
  }