To cite package 'maxLik' in publications use:

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

Corresponding BibTeX entry:

  @Article{,
    title = {maxLik: A package for maximum likelihood estimation in
      {R}},
    author = {Arne Henningsen and Ott Toomet},
    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},
  }