To cite coin in publications use:

The main reference for the framework implemented in coin is:

Torsten Hothorn, Kurt Hornik, Mark A. van de Wiel and Achim Zeileis (2006). A Lego System for Conditional Inference. The American Statistician 60(3), 257-263.

The reference for the implementation approach in coin is:

Torsten Hothorn, Kurt Hornik, Mark A. van de Wiel, Achim Zeileis (2008). Implementing a Class of Permutation Tests: The coin Package. Journal of Statistical Software 28(8), 1-23. URL http://www.jstatsoft.org/v28/i08/.

Corresponding BibTeX entries:

  @Article{,
    title = {A Lego System for Conditional Inference},
    author = {Torsten Hothorn and Kurt Hornik and Mark A. van de Wiel
      and Achim Zeileis},
    journal = {The American Statistician},
    year = {2006},
    volume = {60},
    number = {3},
    pages = {257--263},
  }

  @Article{,
    title = {Implementing a Class of Permutation Tests: The {coin}
      Package},
    author = {Torsten Hothorn and Kurt Hornik and Mark A. van de Wiel
      and Achim Zeileis},
    journal = {Journal of Statistical Software},
    year = {2008},
    volume = {28},
    number = {8},
    pages = {1--23},
    url = {http://www.jstatsoft.org/v28/i08/},
  }