van der Heijden, Peter G. M., and Stef van Buuren. “Looking Back at the Gifi System of Nonlinear Multivariate Analysis”. Journal of Statistical Software 73, no. 4 (September 12, 2016): 1–8. Accessed March 28, 2024. https://www.jstatsoft.org/index.php/jss/article/view/v073i04.