To cite nlstools in publications use:

Florent Baty, Christian Ritz, Sandrine Charles, Martin Brutsche, Jean-Pierre Flandrois, Marie-Laure Delignette-Muller (2015). “A Toolbox for Nonlinear Regression in R: The Package nlstools.” Journal of Statistical Software, 66(5), 1–21. doi:10.18637/jss.v066.i05.

Please cite both the package and R when using them for data analysis. See also ‘citation()’ for citing R.

Corresponding BibTeX entry:

    title = {A Toolbox for Nonlinear Regression in {R}: The Package
    author = {{Florent Baty} and {Christian Ritz} and {Sandrine
      Charles} and {Martin Brutsche} and {Jean-Pierre Flandrois} and
      {Marie-Laure Delignette-Muller}},
    journal = {Journal of Statistical Software},
    year = {2015},
    volume = {66},
    number = {5},
    pages = {1--21},
    doi = {10.18637/jss.v066.i05},