To cite package ‘acs’ in publications use:

  Glenn E (2019). _acs: Download, Manipulate, and Present American
  Community Survey and Decennial Data from the US Census_. R package
  version 2.1.4, , <https://CRAN.R-project.org/package=acs>.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {acs: Download, Manipulate, and Present American Community Survey and
Decennial Data from the US Census},
    author = {Ezra Haber Glenn},
    year = {2019},
    note = {R package version 2.1.4, 
},
    url = {https://CRAN.R-project.org/package=acs},
  }