To cite package 'SixSigma' in publications use:

Emilio L. Cano, Javier M. Moguerza and Andres Redchuk (2012)Six Sigma with R. Springer, New York

Corresponding BibTeX entry:

  @Book{,
    title = {Six Sigma with R},
    author = {Emilio L. Cano and Javier M. Moguerza and Andres
      Redchuk},
    year = {2012},
    publisher = {Springer},
    address = {New York},
    volume = {36},
    series = {Use R!},
  }