Product Differentiation, Search Costs, and Competition in th...     http://home.uchicago.edu/~syverson/mutualfunds5.pdf     tags: stock sp500 historical closing prices of mult indexes     http://www.cboe.com/LearnCenter/pricehistory.xls     tags: vix sp500 data stock The CBOE Volatility Index (VIX) Based on S&P 500 Options Pri...     http://www2.standardandpoors.com/spf/pdf/index/VIX_Final.pdf     tags: vix sp500 stock Compontents and description of S&P 500 index     http://www.stockmorph.com/describe-index/SP%20500.html     tags: sp500 s_p500 Google Answers: pe ratios for the s&p 500, as per Robert Sch...     http://answers.google.com/answers/threadview?id=517700     tags: stock data sp500