To cite nlstools in publications use:

Baty, F. and Ritz, C. and Charles, S. and Brutsche, M. and Flandrois, J.P. and Delignette-Muller, M.L. (2014). A Toolbox for Nonlinear Regression in R: The Package nlstools. under revision at Journal of Statistical Software.

Corresponding BibTeX entry:

  @Article{,
    title = {A Toolbox for Nonlinear Regression in R: The Package
      nlstools},
    author = {F. Baty and C. Ritz and S. Charles and M. Brutsche and
      J.P. Flandrois and M.L. Delignette-Muller},
    journal = {under revision at Journal of Statistical Software},
    year = {2014},
  }