ΜΕΛΕΤΕΣ

http://onlinelibrary.wiley.com/doi/10.1002/jor.20008/pdf

http://www.physther.net/content/86/5/672.short

http://www.ingentaconnect.com/content/adis/smd/2002/00000032/00000013/art00004

http://ajs.sagepub.com/content/34/4/592.short

http://jama.ama-assn.org/content/290/19/2573.short

http://www.ncbi.nlm.nih.gov/pubmed/18515912/