Here are a few medical abstracts on the subject.
http://www.ncbi.nlm.nih.gov/pubmed/1...m&ordinalpos=4
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http://www.ncbi.nlm.nih.gov/pubmed/17606778?ordinalpos=1&itool=EntrezSystem2.PEntrez. Pubmed.Pubmed_ResultsPanel.Pubmed_SingleItemSupl.P ubmed_Discovery_RA&linkpos=2&log$=relatedarticles& logdbfrom=pubmed
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http://www.ncbi.nlm.nih.gov/pubmed/10636366?ordinalpos=1&itool=EntrezSystem2.PEntrez. Pubmed.Pubmed_ResultsPanel.Pubmed_SingleItemSupl.P ubmed_Discovery_RA&linkpos=1&log$=relatedarticles& logdbfrom=pubmed
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http://www.ncbi.nlm.nih.gov/pubmed/1...&ordinalpos=36
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hmm if the links dont work look to your right in the first abstract, it has a listing of the other relevant abstracts and more.
S