To cite landsat in publications use:

Goslee S (2011). “Analyzing Remote Sensing Data in R: The landsat Package.” Journal of Statistical Software, 43(4), 1–25. doi:10.18637/jss.v043.i04.

Corresponding BibTeX entry:

  @Article{,
    title = {Analyzing Remote Sensing Data in {R}: The {landsat}
      Package},
    author = {Sarah C. Goslee},
    journal = {Journal of Statistical Software},
    year = {2011},
    volume = {43},
    number = {4},
    pages = {1--25},
    doi = {10.18637/jss.v043.i04},
  }