deletions | additions       diff --git a/Introduction.tex b/Introduction.tex  index 4d10d24..a82da88 100644  --- a/Introduction.tex  +++ b/Introduction.tex 
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http://www.mathmodels.org/problems/probview.php?probnum=20095  \url{http://www.gams.com/presentations/birthday_ferris.pdf}  \url{http://faculty.csusm.edu/oskoorouchi/silp5.pdf}  \url{ftp://ftp.cs.wisc.edu/pub/dmi/tech-reports/00-01.pdf}  \url{http://www.math.washington.edu/~morrow/mcm/uw25.pdf}