To cite package 'HH' in publications use:

Heiberger RM (2019). HH: Statistical Analysis and Data Display: Heiberger and Holland.. R package version 3.1-37, https://CRAN.R-project.org/package=HH.

To cite the HH book (second edition) in publications use:

Heiberger RM, Holland B (2015). Statistical Analysis and Data Display: An Intermediate Course with Examples in R, Second edition. Springer-Verlag, New York. http://www.springer.com/us/book/9781493921218.

To cite the HH book (first edition) in publications use:

Heiberger RM, Holland B (2004). Statistical Analysis and Data Display: An Intermediate Course with Examples in S-Plus, R, and SAS, First edition. Springer-Verlag, New York. http://www.springer.com/us/book/9781441923202.

To cite likert from HH in publications use:

Heiberger RM, Robbins NB (2014). “Design of Diverging Stacked Bar Charts for Likert Scales and Other Applications.” Journal of Statistical Software, 57(5), 1–32. http://www.jstatsoft.org/v57/i05/.

Corresponding BibTeX entries:

  @Manual{,
    title = {HH: Statistical Analysis and Data Display: Heiberger and
      Holland.},
    author = {Richard M. Heiberger},
    year = {2019},
    note = {R package version 3.1-37},
    url = {https://CRAN.R-project.org/package=HH},
  }
  @Book{,
    title = {Statistical Analysis and Data Display: An Intermediate
      Course with Examples in {R}},
    author = {Richard M. Heiberger and Burt Holland},
    year = {2015},
    publisher = {Springer-Verlag, New York},
    edition = {Second},
    url = {http://www.springer.com/us/book/9781493921218},
  }
  @Book{,
    title = {Statistical Analysis and Data Display: An Intermediate
      Course with Examples in {S-Plus}, {R}, and {SAS}},
    author = {Richard M. Heiberger and Burt Holland},
    year = {2004},
    publisher = {Springer-Verlag, New York},
    edition = {First},
    url = {http://www.springer.com/us/book/9781441923202},
  }
  @Article{,
    title = {Design of Diverging Stacked Bar Charts for Likert Scales
      and Other Applications},
    author = {Richard M. Heiberger and Naomi B. Robbins},
    journal = {Journal of Statistical Software},
    year = {2014},
    volume = {57},
    number = {5},
    pages = {1--32},
    url = {http://www.jstatsoft.org/v57/i05/},
  }