To cite the R package 'dlnm' in publications use:

Gasparrini A. Distributed lag linear and non-linear models in R: the package dlnm. Journal of Statistical Software. 2011; 43(8):1-20. https://doi.org/10.18637/jss.v043.i08

A BibTeX entry for LaTeX users is returned by: toBibtex(citation('dlnm'))

Corresponding BibTeX entry:

  @Article{,
    title = {Distributed lag linear and non-linear models in {R}: the
      package {dlnm}},
    author = {Antonio Gasparrini and Ben Armstrong and Fabian Scheipl},
    journal = {Journal of Statistical Software},
    year = {2011},
    volume = {43},
    number = {8},
    pages = {1--20},
    doi = {10.18637/jss.v043.i08},
    url = {https://doi.org/10.18637/jss.v043.i08},
  }