To cite the package 'GSVA' in publications use:

  Hänzelmann, S., Castelo, R. and Guinney, A. GSVA: gene set variation
  analysis for microarray and RNA-seq data. BMC Bioinformatics, 14:7,
  2013.

A BibTeX entry for LaTeX users is

  @Article{,
    title = {{GSVA}: gene set variation analysis for microarray and {RNA-Seq} data},
    author = {Sonja H{\"a}nzelmann and Robert Castelo and Justin Guinney},
    journal = {BMC Bioinformatics},
    volume = {14},
    pages = {7},
    year = {2013},
    url = {https://doi.org/10.1186/1471-2105-14-7},
    doi = {10.1186/1471-2105-14-7},
  }