To cite gage:

  Luo, W., Friedman, M., Shedden K., Hankenson, K. and Woolf, P GAGE:
  Generally Applicable Gene Set Enrichment for Pathways Analysis. BMC
  Bioinformatics, 2009, 10:161

A BibTeX entry for LaTeX users is

  @Article{,
    author = {{Luo} and {Weijun} and {Friedman} and {Michael} and {Shedden} and {Kerby} and {Hankenson} and {Kurt} and {Woolf} and {Peter}},
    title = {GAGE: generally applicable gene set enrichment for pathway analysis},
    journal = {BMC Bioinformatics},
    year = {2009},
    volume = {10},
    pages = {161},
  }

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