To cite lmtest in publications use:

Achim Zeileis, Torsten Hothorn (2002). Diagnostic Checking in Regression Relationships. R News 2(3), 7-10. URL https://CRAN.R-project.org/doc/Rnews/

Corresponding BibTeX entry:

  @Article{,
    title = {Diagnostic Checking in Regression Relationships},
    author = {Achim Zeileis and Torsten Hothorn},
    journal = {R News},
    year = {2002},
    volume = {2},
    number = {3},
    pages = {7--10},
    url = {https://CRAN.R-project.org/doc/Rnews/},
  }