http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3268359/ http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3268359/ an important scientific paper by Clifford Woolf http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3268359/ http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3268359/