To cite package multtest in publications use:

  K.S Pollard, S. Dudoit, M.J. van der Laan (2005). Multiple Testing
  Procedures: R multtest Package and Applications to Genomics, in
  Bioinformatics and Computational Biology Solutions Using R and
  Bioconductor, R. Gentleman, V. Carey, W. Huber, R. Irizarry, S.
  Dudoit (Editors). Springer (Statistics for Biology and Health
  Series), pp. 251-272.

A BibTeX entry for LaTeX users is

  @Book{,
    title = {Multiple Testing Procedures: R multtest Package and Applications to Genomics, in Bioinformatics and Computational Biology Solutions Using R and Bioconductor},
    year = {2005},
    author = {Katherine S. Pollard and Sandrine Dudoit and Mark J. {van der Laan}},
    publisher = {Springer},
  }