To cite oro.nifti in publications use:

Whitcher B, Schmid VJ, Thornton A (2011). “Working with the DICOM and NIfTI Data Standards in R.” Journal of Statistical Software, 44(6), 1–28. doi:10.18637/jss.v044.i06.

Corresponding BibTeX entry:

  @Article{,
    title = {Working with the {DICOM} and {NIfTI} Data Standards in
      {R}},
    author = {Brandon Whitcher and Volker J. Schmid and Andrew
      Thornton},
    journal = {Journal of Statistical Software},
    year = {2011},
    volume = {44},
    number = {6},
    pages = {1--28},
    doi = {10.18637/jss.v044.i06},
  }