To cite the 'rpql' package in publications use:

  Francis K. C. Hui (2023). rpql: Regularized PQL for Joint Selection
  in GLMMs.R package version 0.8.1.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {rpql: Regularized PQL for Joint Selection in GLMMs},
    author = {Francis K. C. Hui},
    year = {2023},
    note = {R package version 0.8.1},
    encoding = {UTF-8},
  }

  Hui, F.K.C., Mueller, S., and Welsh, A.H. (2017) Joint Selection in
  Mixed Models using Regularized PQL Journal of the American
  Statistical Association, 112, 1323-1333.

A BibTeX entry for LaTeX users is

  @Article{,
    title = {Joint Selection in Mixed Models using Regularized PQL},
    author = {Francis K. C. Hui and Samuel Mueller and A. H. Welsh},
    journal = {Journal of the American Statistical Association},
    year = {2017},
    volume = {112},
    pages = {1323--1333},
    encoding = {UTF-8},
  }