To cite phylogram in publications use:

  Wilkinson SP, Davy SK (2018) phylogram: an R package for phylogenetic
  analysis with nested lists. Journal of Open Source Software 3:790.
  DOI: 10.21105/joss.00790

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {{phylogram}: an R package for phylogenetic analysis with nested lists},
    author = {Shaun P. Wilkinson and Simon K. Davy},
    url = {http://joss.theoj.org/papers/10.21105/joss.00790},
    journal = {Journal of Open Source Software},
    volume = {3},
    pages = {790},
    year = {2018},
    doi = {10.21105/joss.00790},
  }