To cite spdep in publications use:

Roger Bivand, Gianfranco Piras (2015). Comparing Implementations of Estimation Methods for Spatial Econometrics. Journal of Statistical Software, 63(18), 1-36. URL http://www.jstatsoft.org/v63/i18/.

Bivand, R. S., Hauke, J., and Kossowski, T. (2013). Computing the Jacobian in Gaussian spatial autoregressive models: An illustrated comparison of available methods. Geographical Analysis, 45(2), 150-179.

Corresponding BibTeX entries:

  @Article{,
    title = {Comparing Implementations of Estimation Methods for
      Spatial Econometrics},
    author = {Roger Bivand and Gianfranco Piras},
    journal = {Journal of Statistical Software},
    year = {2015},
    volume = {63},
    number = {18},
    pages = {1--36},
    url = {https://www.jstatsoft.org/v63/i18/},
  }
  @Article{,
    title = {Computing the Jacobian in Gaussian spatial autoregressive
      models: An illustrated comparison of available methods},
    author = {Roger Bivand and Jan Hauke and Tomasz Kossowski},
    journal = {Geographical Analysis},
    year = {2013},
    volume = {45},
    number = {2},
    pages = {150--179},
    url = {http://www.jstatsoft.org/v63/i18/},
  }