To cite package ‘Ularcirc’ in publications use:

  David T Humphreys, Nicolas Fossat, Madeleine Demuth, Patrick Tam,
  Joshua Ho.

A BibTeX entry for LaTeX users is

  @Article{,
    title = {Ularcirc},
    author = {David T Humphreys and Nicolas Fossat and Madeleine Demuth and Patrick Tam and Joshua Ho},
    journal = {Nucleic Acids Research},
    year = {2019},
    doi = {https://doi.org/10.1093/nar/gkz718},
    publisher = {Oxford},
    url = {https://academic.oup.com/nar/advance-article/doi/10.1093/nar/gkz718/5552786},
  }