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"There is a significant correlation between excessive daytime sleepiness and lack of vitamin D, U.S. researchers suggest."^^<http://www.w3.org/2001/XMLSchema#string>
<http://www.upi.com/Health_News/2012/12/28/Sleepiness-correlated-to-lack-of-vitamin-D/UPI-80321356745581/?spt=hs&or=hn>