Column historical perspectives

To provide a more comprehensive treatment of the patent literature. Tables II-VI were compiled. The patents cited in these tables are primarily compositional, and for historical perspective, they are listed in chronological order by date of issue. Use only patents are not included, but selected examples of these will be highlighted later. Because the U.S. patents predominate, these are listed first unless there is no U. S. equivalent to a relevant foreign issue. Also, to avoid redundancy, patents that are U.S. divisions of earlier U.S. issues (these would be nearly identical in content and claims), and any frequently cited foreign equivalents of U.S. issues are listed beside their counterparts in an adjacent column in Table II along with their issue dates. 

An exhaustive description of PCA historical and applicative perspectives, including a comparative discussion of PCA with respect to related methods, has been given by Joliffe [26] and Jackson [27] other basic references are the dedicated chapters in Massart s book [28] and Comprehensive Chemometrics [29], and a more didactical view, with reference to the R-project code environment may be found in Varmuza [30] and Wehrens [31]. A description of PCA strictly oriented to spectroscopic data may be found in the Handbook of MR Spectroscopy [32], Beebe [33] and in Davies column in Spectroscopy Europe [34,35] other salient references are Wold et al. [36] and Smilde et al. [37],... 

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