To cite the TideHarmonics package in publications please use:

  Stephenson, A. G. (2016). Harmonic Analysis of Tides Using
  TideHarmonics.  URL:
  https://CRAN.R-project.org/package=TideHarmonics.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {Harmonic Analysis of Tides Using TideHarmonics},
    author = {A. G. Stephenson},
    year = {2016},
    url = {https://CRAN.R-project.org/package=TideHarmonics},
  }

Thank you very much. Have a great day.