To cite nlstools in publications use:

F. Baty and M. L. Delignette-Muller (2013), nlstools: tools for nonlinear regression diagnostics.

Corresponding BibTeX entry:

  @Manual{,
    title = {nlstools: tools for nonlinear regression diagnostics},
    author = {Florent Baty and Marie-Laure Delignette-Muller},
    year = {2013},
    note = {R package version 0.0-15},
  }