To cite the topdownr package in publications use:

  P.V. Shliaha, S. Gibb, V. Gorshkov, M.S. Jespersen, G.R. Andersen, D.
  Bailey, J. Schwartz, S. Eliuk, V. Schwämmle, and O.N. Jensen. 2018.
  Maximizing Sequence Coverage in Top-Down Proteomics By Automated
  Multi-modal Gas-phase Protein Fragmentation. Analytical Chemistry.
  DOI: 10.1021/acs.analchem.8b02344

A BibTeX entry for LaTeX users is

  @Article{topdownr,
    title = {Maximizing Sequence Coverage in Top-Down Proteomics By Automated Multi-modal Gas-phase Protein Fragmentation.},
    author = {Pavel Vyacheslavovich Shliaha and Sebastian Gibb and Vladimir Gorshkov and Malena Schack Jespersen and Gregers R. Andersen and Derek Bailey and Jacob Schwartz and Shannon Eliuk and Veit Schwämmle and Ole Nørregaard Jensen},
    volume = {90},
    number = {21},
    pages = {12519--12526},
    year = {2018},
    doi = {10.1021/acs.analchem.8b02344},
    url = {https://pubs.acs.org/doi/10.1021/acs.analchem.8b02344},
    eprint = {https://pubs.acs.org/doi/pdf/10.1021/acs.analchem.8b02344},
    journal = {Analytical Chemistry},
    publisher = {American Chemical Society},
  }