To cite ade4TkGUI in publications use this reference:

  Jean Thioulouse and Stéphane Dray (2007). Interactive Multivariate
  Data Analysis in R with the ade4 and ade4TkGUI Packages. Journal of
  Statistical Software. 22(5): 1-14.

A BibTeX entry for LaTeX users is

  @Article{,
    title = {Interactive Multivariate Data Analysis in R with the ade4 and ade4TkGUI Packages},
    author = {Jean Thioulouse and St\'ephane Dray},
    journal = {Journal of Statistical Software},
    year = {2007},
    volume = {22},
    pages = {1-14},
    number = {5},
  }

  Thioulouse J, Dray S, Dufour A, Siberchicot A, Jombart T, Pavoine S
  (2018). _Multivariate Analysis of Ecological Data with ade4_.
  Springer. doi:10.1007/978-1-4939-8850-1
  <https://doi.org/10.1007/978-1-4939-8850-1>.

A BibTeX entry for LaTeX users is

  @Book{,
    title = {Multivariate Analysis of Ecological Data with {ade4}},
    author = {Jean Thioulouse and St\'ephane Dray and Anne--B\'eatrice Dufour and Aur\'elie Siberchicot and Thibaut Jombart and Sandrine Pavoine},
    year = {2018},
    publisher = {Springer},
    doi = {10.1007/978-1-4939-8850-1},
  }