To cite package 'maxLik' in publications use:

  Toomet O, Henningsen A (2011). “maxLik: A package for maximum
  likelihood estimation in R.” _Computational Statistics_, *26*(3),
  443-458. doi:10.1007/s00180-010-0217-1
  <https://doi.org/10.1007/s00180-010-0217-1>.
  <http://dx.doi.org/10.1007/s00180-010-0217-1>.

A BibTeX entry for LaTeX users is

  @Article{,
    title = {maxLik: A package for maximum likelihood estimation in {R}},
    author = {Ott Toomet and Arne Henningsen},
    journal = {Computational Statistics},
    year = {2011},
    volume = {26},
    number = {3},
    pages = {443-458},
    doi = {10.1007/s00180-010-0217-1},
    url = {http://dx.doi.org/10.1007/s00180-010-0217-1},
  }