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To put the a=ticles in perspective, it is best to briefly review the history of suc~ modeling. The first was initiated by Herman Helmholtz in the 1880's, whose theories dominated the subject for years.
When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.