To cite package ‘VennDiagram’ in publications use:

  Chen, H., Boutros, P.C. VennDiagram: a package for the generation of
  highly-customizable Venn and Euler diagrams in R. BMC Bioinformatics
  12, 35 (2011). https://doi.org/10.1186/1471-2105-12-35

A BibTeX entry for LaTeX users is

  @Article{,
    title = {VennDiagram: a package for the generation of highly-customizable Venn and Euler diagrams in R},
    journal = {BMC Bioinformatics},
    doi = {10.1186/1471-2105-12-35},
    url = {https://doi.org/10.1186/1471-2105-12-35},
    volume = {12},
    number = {35},
    year = {2011},
    month = {January},
    day = {26},
    issn = {1471-2105},
    author = {Hanbo Chen and Paul C Boutros},
  }