To cite the envirem package in publications, use:

Title, P.O., Bemmels, J.B. 2017. ENVIREM: An expanded set of bioclimatic and topographic variables increases flexibility and improves performance of ecological niche modeling. Ecography<doi:10.1111/ecog.02880>

Corresponding BibTeX entry:

  @Article{,
    title = {ENVIREM: An expanded set of bioclimatic and topographic
      variables increases flexibility and improves performance of
      ecological niche modeling},
    author = {PO Title and JB Bemmels},
    journal = {Ecography},
    year = {2017},
  }