To cite the ReactomeGSA in publications use:

  J Griss, G Viteri, K Sidiropoulos, V Nguyen, A Fabregat, and H
  Hermjakob (2020). bioRxiv ReactomeGSA - Efficient Multi-Omics
  Comparative Pathway Analysis. doi: 10.1101/2020.04.16.044958

A BibTeX entry for LaTeX users is

  @Article{,
    title = {ReactomeGSA - Efficient Multi-Omics Comparative Pathway Analysis},
    author = {Johannes Griss and Guilherme Viteri and Konstantinos Sidiropoulos and Vy Nguyen and Antonio Fabregat and Henning Hermjakob},
    journal = {bioRxiv},
    year = {2020},
    doi = {10.1101/2020.04.16.044958},
    url = {https://www.biorxiv.org/content/early/2020/04/18/2020.04.16.044958},
  }