To cite BB in publications use:

  Ravi Varadhan, Paul Gilbert (2009). “BB: An R Package for Solving a
  Large System of Nonlinear Equations and for Optimizing a
  High-Dimensional Nonlinear Objective Function.” _Journal of
  Statistical Software_, *32*(4), 1-26.
  <https://www.jstatsoft.org/v32/i04/>.

A BibTeX entry for LaTeX users is

  @Article{,
    title = {{BB}: An {R} Package for Solving a Large System of Nonlinear Equations and for Optimizing a High-Dimensional Nonlinear Objective Function},
    author = {{Ravi Varadhan} and {Paul Gilbert}},
    journal = {Journal of Statistical Software},
    year = {2009},
    volume = {32},
    number = {4},
    pages = {1--26},
    url = {https://www.jstatsoft.org/v32/i04/},
  }