The reference for the 'filehash' package is:

Peng RD (2006). “Interacting with data using the filehash package,” R News, 6 (4), 19--24.

Corresponding BibTeX entry:

  @Article{,
    title = {Interacting with data using the filehash package},
    author = {Roger D. Peng},
    journal = {R News},
    year = {2006},
    volume = {6},
    number = {4},
    pages = {19--24},
    url = {http://CRAN.R-project.org/doc/Rnews/},
  }