To cite the ensembldb package please use:

  Rainer J, Gatto L, Weichenberger CX (2019) ensembldb: an R package to
  create and use Ensembl-based annotation resources. Bioinformatics.
  doi:10.1093/bioinformatics/btz031

A BibTeX entry for LaTeX users is

  @Article{,
    title = {ensembldb: an R package to create and use Ensembl-based annotation resources.},
    author = {Johannes Rainer and Laurent Gatto and Christian X. Weichenberger},
    year = {2019},
    journal = {Bioinformatics},
    doi = {10.1093/bioinformatics/btz031},
    url = {https://academic.oup.com/bioinformatics/advance-article/doi/10.1093/bioinformatics/btz031/5301311},
  }