Thank you very much Rick. This post and that of the Cholesky transformation helped me very much for a clustering I have been doing. I need to give a reference for a paper, and I was wondering if you could indicate a reference of a publication to refer to for indicating that "The Euclidean distance calculated on the dataset Y is equivalent to the Mahalanobis distance calculated in X." (Here, Y is the data scaled with the inverse of the Cholesky transformation). Σ_X=LL^T Y=XL^(-1) Where Σ_X is the variance-covariance matrix of the environmental covariates sample X, L is the Cholesky factor of Σ_X, a lower triangular matrix with positive diagonal values, and Y is the rescaled covariates dataset. Have you got any reference I could cite? Thanks in advance.