To cite spikeslab in publications use:

Ishwaran H., Rao J.S. and Kogalur U.B. (2013). spikeslab : Prediction and variable selection using spike and slab regression, R package version 1.1.5.
Ishwaran H. and Rao J.S. (2005). Spike and slab variable selection: frequentist and Bayesian strategies.Ann. Statist. 33(2), 730--773.
Ishwaran H. and Rao J.S. (2010). Generalized ridge regression: geometry and computational solutions when p is larger than n.Manuscript.

Corresponding BibTeX entries:

  @Manual{,
    title = {spikeslab : Prediction and variable selection using spike
      and slab regression},
    author = {H. Ishwaran and J.S. Rao and U.B. Kogalur},
    publisher = {manual},
    year = {2013},
    note = {R package version 1.1.5},
    url = {http://cran.r-project.org/web/packages/spikeslab/},
    pdf =
      {http://cran.r-project.org/web/packages/spikeslab/spikeslab.pdf},
  }
  @Article{,
    title = {Spike and slab variable selection: frequentist and
      Bayesian strategies},
    author = {H. Ishwaran and J.S. Rao},
    journal = {Ann. Statist.},
    year = {2005},
    volume = {33},
    number = {2},
    pages = {730--773},
    url = {http://arXiv.org/abs/math/0505633v1},
    pdf = {http://arxiv.org/pdf/math.ST/0505633},
  }
  @Article{,
    title = {Generalized ridge regression: geometry and computational
      solutions when p is larger than n},
    author = {H. Ishwaran and J.S. Rao},
    journal = {Manuscript},
    year = {2010},
  }