To cite GOstats in publications use:

  S Falcon and R Gentleman. Using GOstats to test gene lists for GO
  term association. Bioinformatics, 23(2):257-8, 2007.

A BibTeX entry for LaTeX users is

  @Article{,
    author = {S Falcon and R Gentleman},
    title = {Using {G}{O}stats to test gene lists for {G}{O} term association.},
    journal = {Bioinformatics},
    year = {2007},
    volume = {23},
    number = {2},
    pages = {257-8},
  }