To cite spThin in publications use:

  Aiello-Lammens, M. E., Boria, R. A., Radosavljevic, A. , Vilela, B.
  and Anderson, R. P. (2015). spThin: an R package for spatial thinning
  of species occurrence records for use in ecological niche models.
  Ecography, 38: 541-545. URL
  https://onlinelibrary.wiley.com/doi/10.1111/ecog.01132.

A BibTeX entry for LaTeX users is

  @Article{,
    title = {{spThin}: an {R} package for spatial thinning of species occurrence records for use in ecological niche models},
    author = {Matthew E. Aiello-Lammens and Robert A. Boria and Aleksandar Radosavljevic and Bruno Vilela},
    journal = {Ecography},
    year = {2015},
    volume = {38},
    number = {5},
    pages = {541--545},
    url = {https://onlinelibrary.wiley.com/doi/10.1111/ecog.01132},
  }