To cite calculus in publications use:

Guidotti E (2022). “calculus: High-Dimensional Numerical and Symbolic Calculus in R.” Journal of Statistical Software, 104(5), 1–37. doi:10.18637/jss.v104.i05.

Corresponding BibTeX entry:

  @Article{,
    title = {{calculus}: High-Dimensional Numerical and Symbolic
      Calculus in {R}},
    author = {Emanuele Guidotti},
    journal = {Journal of Statistical Software},
    year = {2022},
    volume = {104},
    number = {5},
    pages = {1--37},
    doi = {10.18637/jss.v104.i05},
  }