To cite GrassmannOptim in publications use:

Kofi P. Adragni, R. Dennis Cook, Seongho Wu (2012). GrassmannOptim: An R Package for Grassmann Manifold Optimization. Journal of Statistical Software, 50(5), 1-18. URL http://www.jstatsoft.org/v50/i05/.

Corresponding BibTeX entry:

  @Article{,
    title = {{GrassmannOptim}: An {R} Package for Grassmann Manifold
      Optimization},
    author = {Kofi P. Adragni and R. Dennis Cook and Seongho Wu},
    journal = {Journal of Statistical Software},
    year = {2012},
    volume = {50},
    number = {5},
    pages = {1--18},
    url = {http://www.jstatsoft.org/v50/i05/},
  }