http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2413110/
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2719171/
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3091506/
http://cardiovascres.oxfordjournals.org/content/80/1/9.full