To cite the UNF package in publications use:

Altman, M., Gill, J. and M.P. McDonald (2003) Numerical Issues in Statistical Computing for the Social Scientist. John Wiley and Sons, New York. (Software version: R Package, UNF, version 1.13) ISBN 0-471-23633-0.

Corresponding BibTeX entry:

  @Book{,
    title = {Numerical Issues in Statistical Computing for the Social
      Scientist},
    author = {M. Altman and J. Gill and M.P. McDonald},
    publisher = {John Wiley and Sons},
    edition = {First},
    address = {New York},
    year = {2003},
    isbn = {ISBN 0-471-23633-0},
    note = {Software: R Package, UNF, version 1.13 },
    url = {http://www.hmdc.harvard.edu/micah_altman/numal/},
  }