PCA
http://cmp.felk.cvut.cz/~hlavac/TeachPresEn/11ImageProc/15PCA.pdf
http://stats.stackexchange.com/questions/2691/making-sense-of-principal-component-analysis-eigenvectors-eigenvalues
PCA for Images
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1679-45082012000200004
Mulivariate Tools
https://www.gitbook.com/book/svkucheryavski/mdatoolsm/details
PLS
http://www.eupigclass.net/Work1_8.htm
Multivariate Techniques
http://folk.uio.no/ohammer/past/multivar.html
