This article was published in an Elsevier journal. The attached copy is furnished to the author for non-commercial research and education use, including for instruction at the author’s institution, sharing with colleag

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Date: 2009-12-16 14:33:59		This article was published in an Elsevier journal. The attached copy is furnished to the author for non-commercial research and education use, including for instruction at the author’s institution, sharing with colleag Add to Reading List Source URL: www.math.niu.edu Download Document from Source Website File Size: 861,02 KB Share Document on Facebook