To cite R/SSN in publications use:

Ver Hoef, J. M. and Peterson, E. E. (2010) A moving average approach for spatial statistical models of stream networks (with discussion). Journal of the American Statistical Association 105:6-18.<doi:10.1198/jasa.2009.ap08248>

Jay M. Ver Hoef, Erin E. Peterson, David Clifford, Rohan Shah (2014). SSN: An R Package for Spatial Statistical Modeling on Stream Networks. Journal of Statistical Software, 56(3), 1-43. URL http://www.jstatsoft.org/v56/i03/.

Corresponding BibTeX entries:

  @Article{,
    title = {A moving average approach for spatial statistical models
      of stream networks (with discussion)},
    author = {Jay M. {Ver Hoef} and Erin E. Peterson},
    journal = {Journal of the American Statistical Association},
    year = {2010},
    volume = {105},
    pages = {6-18},
  }
  @Article{,
    title = {{SSN}: An {R} Package for Spatial Statistical Modeling on
      Stream Networks},
    author = {Jay M. Ver Hoef and Erin E. Peterson and David Clifford
      and Rohan Shah},
    journal = {Journal of Statistical Software},
    year = {2014},
    volume = {56},
    number = {3},
    pages = {1--45},
    url = {http://www.jstatsoft.org/v56/i03/},
  }