To cite cleanNLP in publications use:

  Taylor Arnold (2017). A Tidy Data Model for Natural Language
  Processing using cleanNLP. The R Journal, 9(2), 1-20. URL
  https://journal.r-project.org/archive/2017/RJ-2017-035/index.html.

A BibTeX entry for LaTeX users is

  @Article{,
    title = {A Tidy Data Model for Natural Language Processing using cleanNLP},
    author = {Taylor Arnold},
    journal = {The R Journal},
    year = {2017},
    volume = {9},
    number = {2},
    pages = {1--20},
    url = {https://journal.r-project.org/archive/2017/RJ-2017-035/index.html},
  }