This R package is based on the Pscan web platform described in the
following publication

  Zambelli F, Pesole G, Pavesi G (2009). “Pscan: finding
  over-represented transcription factor binding site motifs in
  sequences from co-regulated or co-expressed genes.” _Nucleic Acids
  Research_, *37*, W247-W252. doi:10.1093/nar/gkp464
  <https://doi.org/10.1093/nar/gkp464>.

A BibTeX entry for LaTeX users is

  @Article{,
    title = {Pscan: finding over-represented transcription factor binding site motifs in sequences from co-regulated or co-expressed genes.},
    author = {Federico Zambelli and Graziano Pesole and Giulio Pavesi},
    journal = {Nucleic Acids Research},
    year = {2009},
    volume = {37},
    pages = {W247-W252},
    doi = {10.1093/nar/gkp464},
  }